Cardiac Flashcards
How Long Should Noncardiac Surgery
Be Delayed Following Acute Myocardial
Infarction?
○ The American College of Cardiology and American Heart Association (ACC/AHA) recommend avoidance of surgery for 60 days after acute MI.
○ This is partly based on a large retrospective study of 563,842 patients with recent MI having hip surgery, cholecystectomy, elective abdominal aortic aneurysm repair, or lower limb amputation.
○ The rate of postoperative MI decreased significantly as the interval between preoperative MI and surgery increased (0–30 days = 32.8%; 31–60 days = 18.7%; 61–90 days = 8.4%; and 91–180 days = 5.9%).
○ The 30-day mortality rate associated
with postoperative MI decreased in a similar fashion (0–30 days = 14.2%; 31–60 days = 11.5%;
1–90 days = 10.5%; and 91–180 days = 9.9%).
○ It is worth noting that the elevated postoperative mortality risk when
undergoing surgery 6 months after MI (9.9%) is greater than the 30-day mortality after acute coronary syndrome (ACS)
from all causes by a factor of 2–3.
○ In patients undergoing surgery after recent MI, revascularization by percutaneous coronary intervention (PCI)/stenting or coronary artery bypass surgery has been shown to improve postoperative infarction, and 30-day and 1-year mortality rate by at least50% [4].
○ However, citing a lack of extensive evidence, the ACC/AHA recommend against routine coronary revascularization before noncardiac surgery outside of the current practice guidelines for coronary artery bypass grafting (CABG) and PCI
What Is the Difference Between Type 1 and Type 2 Myocardial Infarction?
○ Type 1 MI is a spontaneous MI in the setting of atherothrombotic coronary artery disease.
• Type 1 MI is what we usually consider a traditional MI.
• It is usually secondary to plaque
rupture or erosion.
○ Type 2 MI is due to a mismatch between myocardial oxygen supply and demand.
• Coronary artery disease may be
present, but it is not the primary cause. • Common underlying etiological causes include coronary artery dissection, spasm, emboli, anemia, arrhythmias, and hypotension.
• The key diagnostic features of type 2 MI are an elevated and changing
troponin, clinical features not consistent with type 1 MI, presence of clinical conditions known to disrupt oxygen supply/demand, e.g., tachycardia, and absence of causes
indicating other nonischemic causes of raised troponin, e.g., myocarditis
What Is Acute Coronary Syndrome?
“Acute coronary syndrome” is an umbrella term for myocardial infarction (STEMI or NSTEMI) and unstable angina.
• It is a medical emergency and necessitates referral to a cardiologist for evaluation and treatment that may include revascularization and subsequent initiation of antiplatelet therapy
What Complications Is the Patient
with Ischemic Heart Disease Subject
to in the Perioperative Period?
• Perioperative MI
• Cardiac failure
• Cardiac arrest
• Arrhythmia
• Stroke
• Death
What Are the Characteristic
Features of Perioperative
Myocardial Infarction?
○ Unlike spontaneously occurring MIs, it is quite usual for the patient experiencing a perioperative MI to be asymptomatic .
○ In a study of 2546 patients at increased cardiovascular risk undergoing noncardiac surgery, only 6% of patients with postoperative MI reported chest pain (the incidence of post-operative MI was 16%).
○ Because the typical symptoms of
myocardial ischemia are not exhibited, the diagnosis is easily missed.
○ Perioperative MI has a poor prognosis; despite its asymptomatic nature, 30-day mortality (10%) may be higher than that associated with non-postoperative MI (30-day
mortality for NSTEMI and STEMI is approximately 2% and 2–10%, respectively.
○ The highest risk of death is in the
first 48 postoperative hours.
○ Because of the silent nature of
postoperative ischemia, routine monitoring of troponin level is recommended in at-risk patients for the first 72 postoperative hours
What Is Myocardial Injury After Noncardiac Surgery (MINS)?
○ Myocardial injury after noncardiac surgery (MINS) is defined as prognostically relevant myocardial injury due to ischemia occurring within 30 days of noncardiac surgery.
○ Diagnosis is made in the presence of elevated troponin with or without ischemic symptoms or ECG changes.
○ MINS is common with a reported incidence of up to 18% and is associated with a high 30-day mortality rate (4.1%).
Describe a General Approach to
Evaluation of a Patient with a History
of Acute Coronary Syndrome Who Is
Scheduled to Undergo Noncardiac Surgery?
• Has the patient had an ST elevation MI (STEMI) or a non-ST elevation MI (NSTEMI), and if so, was this a recent occurrence? Is ongoing unstable angina a concern?
• What is the estimated risk of a major adverse coronary event (MACE)?
• When is it appropriate to order further investigations, e.g., exercise or pharmacological stress testing, echocardiography or angiography?
• What is the patient’s functional capacity, and how does it relate to decision-making with regard to further investigations?
• When should revascularization be considered preoperatively?
Having Decided That Our Patient Has
Established Coronary Artery Disease, How
Do We Negotiate Step 2 of the ACC/AHA?
○ This patient’s surgery, though time-sensitive, is not an emergency.
○ There is time for further evaluation.
○ In this case, the patient can be referred to a cardiologist for optimization according to what the ACC/AHA refer to as “guideline-
directed medical therapy” for STEMI and NSTEMI
How Is the Risk of a Major Cardiovascular Complication Estimated Prior to Surgery?
○ A number of risk-prediction tools, e.g., Revised Cardiac Risk Index (RCRI) and the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) Surgical Risk Calculator are used to estimate the risk of non-fatal
perioperative MI or cardiovascular death (together, non-fatal
perioperative MI and cardiovascular death occasionally form a composite end-point in clinical trials, referred to as major adverse cardiovascular event [MACE])
○ The ACS NSQIP is a web-based universal risk calculator that is predictive for 18 disparate complications, including MI and cardiac arrest.
○ A separate risk calculator, the American College of Surgeons Myocardial Infarction and Cardiac Arrest Calculator (ACS MICA), looks specifically at perioperative cardiac events.
○ All risk-prediction tools incorporate elements of risk related to patient history in combination with surgical complexity.
○ Level B evidence (data derived from a single randomized trial or nonrandomized studies) suggests that patients found
to be at low risk of MACE do not benefit from further investigations prior to elective surgery
Revised Cardiac Risk Index or NSQIP Surgical Risk Calculator—Which Is Better for Assessing Perioperative Risk?
○ Critics of ACS NSQIP and MICA maintain that they likely underestimate cardiac risk because patients in contributing studies did not undergo perioperative troponin testing.
○ Similarly, neither NSQIP risk calculator has undergone external validation in a study that systematically monitored troponin measurements after noncardiac surgery
○ In contrast, the RCRI has been externally validated, and its predictive value was found to be significant in all types of elective noncardiac surgery except for abdominal aortic aneurysm repair.
○ A further criticism of the NSQIP calculators relates to the definition of MI in the studies used to derive the NSQIP risk indices, which included only STEMIs or a large increase in troponin (>3 times normal) that occurred in symptomatic patients.
○ As we saw earlier, most postoperative infarcts tend to be of the NSTEMI variety and silent.
○ Advocates for both NSQIP risk calculators point to the large patient numbers and multicenter methodology used in their development: over 200,000 patients from more than 250 hospitals for ACS MICA and over 1.4 million patients from 393 hospitals for ACS NSQIP.
○ The RCRI was developed from a prospective single-center cohort of 4315 patients.
○ In summary, the RCRI is a simple and easy-to-use risk prediction tool, while the ACS NSQIP provides a more detailed and wider ranging assessment of risk, beyond cardiovascular risk, which takes specific surgical procedures into account.
○ There is no evidence that one is clearly superior.
What Do the RCRI and the NSQIP Surgical
Risk Calculator Tell Us About Our Patient?
○ He has an RCRI score of 5 (all parameters are present except history of cerebrovascular disease).
○ This gives him a 15% risk estimate for MI, cardiac arrest, or death within 30 days of surgery.
○ According to the NSQIP surgical
risk calculator, he has a 5.6% risk of MI or cardiac arrest up to 30 days after surgery.
Having Established That the Patient Is at Risk
for a Major Cardiac Complication, What Are
the Next Steps in Assessment?
○ The next step in the evaluation of the high-risk patient is determination of functional capacity.
○ The long-established metabolic equivalent of task (MET) score is frequently used for this (Table 2.5).
○ The Duke Activity Status Index (DASI)
is a self-assessment tool consisting of 12 questions relating to activities of daily living which appears to be a more objective measure of functional capacity.
○ It has been shown to be a better predictor of death or MI within 30 days of major elective noncardiac surgery.
○ A finding of poor functional capacity warrants pharmacological stress testing (myocardial perfusion imaging or dobutamine stress echocardiography) if surgery is not urgent and the patient is a willing and appropriate candidate for revascularization.
○ In other words, we must be reasonably certain that stress testing will change our approach to perioperative care.
○ Patients who are at increased cardiac risk with unknown functional capacity may proceed to exercise stress testing if, similarly, it will alter preoperative optimization.
○ Routine exercise stress testing is not beneficial for patients undergoing low-risk surgery or for patients deemed to be low risk for MACE.
Is Echocardiographic Assessment of Left
Ventricular Function of Benefit?acs
○ There appears to be little value in performing preoperative echocardiography in a non-discriminatory manner in cardiac patients.
○ ACC/AHA recommend against routine
preoperative echocardiographic assessment of LV function except for investigation of dyspnea of unknown origin, worsening dyspnea in the heart failure patient, and reassessment of LV function in clinically stable patients with previously documented LV dysfunction who have not been assessed within the past year.
○ The Canadian Cardiovascular Society recommends against performing resting echocardiography to enhance perioperative cardiac risk estimation.
○ The two exceptions to this are clinical
evidence of an undiagnosed severe obstructive intracardiac abnormality (e.g., aortic stenosis, mitral stenosis, hypertrophic obstructive cardiomyopathy) or severe pulmonary hypertension
Which Noninvasive Imaging Technique—
Stress Radionuclide Myocardial Perfusion
Imaging or Stress Echocardiography—Is
Preferable?
○ Practical or logistical concerns often dictate which noninvasive stress imaging test in performed, e.g., local availability,
expertise, patient body habitus (precluding adequate echocardiography views), and cost.
○ Both imaging techniques have similar diagnostic accuracy.
○ A single meta-analysis demonstrated that stress myocardial perfusion imaging using single-photon emission computed tomography (SPECT) and stress echocardiography had similar sensitivities but stress echocardiography had higher specificity for detection of coronary artery disease.
○ Both myocardial perfusion imaging and stress echocardiography had better discriminatory capabilities than exercise stress testing
When Is Preoperative Angiography Indicated?
○ The indications for angiography before surgery are similar to those in a nonsurgical setting, i.e., high-risk features seen on noninvasive imaging.
○ Examples include a strongly positive exercise stress test, imaging study suggestive of a significant amount of viable myocardium at risk, and multiple reversible defects.
What Are the Indications for Revascularization in the High-Risk
Cardiac Patient Awaiting Noncardiac
Surgery?
○ Recommendations for revascularization are the same as those for all patients with coronary artery disease, i.e., there are no RCTs which demonstrate perioperative benefit from revascularization.
○ Indications for coronary revascularization (including the specific indications for CABG versus PCI) are beyond the scope of this book, but the decision to proceed is generally based upon the location and severity of the lesion, e.g., significant left main coronary artery disease, the number of diseased arteries, and the presence of left ventricular dysfunction.
○ It should be borne in mind that patients undergoing PCI will need to have surgery
deferred while on antiplatelet therapy.
For How Long Should Surgery Be Postponed in a Patient Who Has Undergone Coronary Artery Stenting?
○ Premature discontinuation of dual antiplatelet therapy (DAPT) in PCI patients can lead to stent thrombosis, MI, and death.
○ General recommendations for DAPT are extensively reviewed in the 2016 ACC/AHA Guideline Focused Update on Duration of Dual Antiplatelet Therapy in Patients with Coronary Artery Disease and the 2018 Canadian Cardiovascular Society/Canadian Association of Interventional Cardiology Focused Update of the Guidelines for the Use of Antiplatelet Therapy.
○ Patients with ACS who have undergone PCI with bare metal stent (BMS) or drug-eluting stent (DES) will require DAPT with aspirin and an ADP receptor antagonist, e.g., clopidogrel, ticagrelor, or prasugrel, for at least 12 months.
○ According to the more recently updated Canadian guidelines, patients who have elective PCI in the absence of ACS will require DAPT for 6 months in the form of aspirin and clopidogrel, if not at high risk of bleeding.
○ If risk of bleeding is high, DAPT is required for 1 month with BMS and
3 months for DES.
○ This is an evolving area as stent morphology and therapeutics are constantly being amended with one goal being to reduce the duration of DAPT.
○ Patients with a stent requiring elective noncardiac surgery should be evaluated bearing in mind the following considerations: urgency of surgery, risk of bleeding related to antiplatelet therapy, stent thrombosis in the absence of antiplatelet therapy, and type of stent, i.e., BMS versus DES.
○ Each patient should be managed on a case-by-case basis in consultation with the patient’s interventional cardiologist.
○ Recommendations in general are based on low-quality evidence. Canadian and US guidelines are provided
ACS in Our Patient Was Treated
with Intravenous Heparinization
and DAPT. If He Had Not Experienced Frank
Hematuria, For How Long Should DAPT Have
Been Continued?
Patients with medically managed ACS who are not
revascularized are treated with DAPT for at least 12 months
if bleeding complications do not occur
How Can Perioperative Cardiac Risk
Be Medically Modified?acs
○ The question of whether to initiate pharmacological agents or to maintain those on which the patient is already
established is an ever-changing domain.
○ A summary of current recommendations from the ACC/AHA and Canadian Cardiovascular Society is presented in Table 2.8
Should This Patient Have BNP Measured Preoperatively as a Screening Measure for Postoperative Myocardial Injury?
○ The Canadian Cardiovascular Society recommends measuring BNP before noncardiac surgery when RCRI ≥1, if the patient is 65 years or older or is 45–64 years with significant cardiovascular disease.
○ Patients with preoperative BNP >92 pg/mL should have daily pos-toperative troponin measurement for 48–72 hours to detect silent ischemia.
○ However, considering our patient had a recent episode of ACS with congestive cardiac failure and a recent BNP value of 464, it is of doubtful value.
○ In this case, daily postoperative troponin measurement is indicated regardless
True/False
Elective surgery should be deferred for at least
6 months after acute myocardial infarction.
F
True/False
By definition, myocardial injury after noncardiac
surgery occurs within 30 days of surgery.
T
True/False
Most perioperative myocardial infarcts are
symptomatic.
F
True/False
Revised Cardiac Risk Index (RCRI) is a superior peri-
operative cardiac risk prediction tool when compared
with the American College of Surgeons National
Surgical Quality Improvement Program (ACS NSQIP)
F
True/False
RCRI uses patient functional capacity as a variable
when calculating perioperative cardiac risk.
F
What Are the Physiologic Effects of a Fontan Procedure?
○ The Fontan procedure is generally used in patients who have
univentricular physiology such as hypoplastic left heart, tricuspid atresia, or a double inlet left ventricle.
○ A Fontan shunt bypasses the right ventricle and provides passive, non-pulsatile flow from the superior vena cava and inferior vena cava (IVC) to the pulmonary arteries.
○ Pulmonary blood flow is dependent on the difference between the central venous pressure (CVP) and the pulmonary venous atrium or transpulmonary gradient (TPG).
○ In terms of hemodynamic goals, it is reasonable to strive for a CVP of 10–15 and TPG of 5–10 mmHg
What Are Some of the Systemic Complications in the Patient with Failing Fontan Physiology?
• CARDIAC
- Eventually pulmonary vascular resistance (PVR) increases, and it becomes difficult to maintain cardiac output.
- Patients may develop systolic and diastolic dysfunction of the systemic ventricle, atrioventricular valve regurgitation, pulmonary hypertension, and significant arrhythmias.
- As the systemic ventricular end-diastolic pressure rises, the common atrial pressure will also rise, and in turn, a higher CVP will be required to maintain cardiac output (CO).
- Increased risk of arrhythmias and conduction abnormalities such as SVT or sinoatrial node dysfunction is often due to atrial scarring, dilation, and hypertrophy.
• RESPIRATORY
- Plastic Plastic bronchitis, restrictive lung disease, and/or reduced aerobic capacity due to nonpulsatile pulmonary flow and limited ability to augment pulmonary flow and pressure.
• HEPATIC
- Chronic elevations in CVP and decreased CO may result in Fontan-associated liver disease (FALD), elevated transaminases, cirrhosis, as well as factor loss, hypoalbuminemia, and hypogammaglobulinemia from protein-losing enteropathy (PLE).
- Therefore, the patient’s coagulation status may range from pro(thromboembolic) to anticoagulated.
• RENAL
- Hypoalbuminemia may also increase the risk of perioperative renal dysfunction.
• HEMATOLOGIC
- From a hematological standpoint, patients may develop erythrocytosis secondary to chronic hypoxemia.
- Hyperviscosity may be exacerbated in the setting of dehydration or fasting preoperatively.
- Transfusion triggers in cyanotic patients may need to be altered to maintain tissue oxygenation.
- A hematocrit >0.55 may falsely elevate the INR.
- Adult congenital heart disease patients may also develop acquired von Willebrand disease.
• NEUROLOGIC
- Developmental delay or cognitive impairment may also present a challenge.
- Patient anxiety is a common feature in those transitioning from pediatric to adult care.
• AIRWAY
- Securing the airway may present an issue if there is a history of subglottic stenosis secondary to prior prolonged intubation or an associated syndrome such as trisomy 21, DiGeorge, or Cornelia de Lange.
- The possibility of tracheomalacia should also be considered if dilated pulmonary arteries compress the trachea.
- Prior coarctation/aortic arch repair may cause recurrent laryngeal nerve dysfunction.
How Should This Patient with Fontan circulation Be Evaluated Preoperatively?
• Preoperative evaluation should involve interdisciplinary collaboration with the attending surgeon, adult congenital cardiologist, cardiac anesthesiologist, adult congenital cardiac surgeon, and electrophysiologist.
- Moderate- or high-risk lesions are ideally managed at a center with expertise for advanced monitoring and management.
• Detailed knowledge is required of the native congenital cardiac lesion and prior palliative and reparative interventions.
– Identify specific anatomical repairs and any residual hemodynamic issues.
– Establish whether prior procedures may affect proposed sites for peripheral/central venous/arterial or extracorporeal membrane oxygenation (ECMO) access.
– Review imaging of upper/lower limb vessels to assess size and patency.
• Establish current cardiopulmonary reserve.
– Review investigations including cardiopulmonary testing (VO2 max studies), echocardiography, cardiac catheterization, MRI, and CT/CT angiography.
– Evaluate arrhythmia control, implanted devices such as pacemakers or automated implantable cardioverter-defibrillators, and perioperative management in conjunction with an electrophysiologist.
• Consider the proposed surgical procedure and potential hemodynamic effects, including potential for increased bleeding in the setting of elevated venous pressure
What Factors May Influence Planning for Sites of Invasive Monitoring? BT shunt
• Prior BT shunt – this surgical connection between the ipsilateral subclavian and pulmonary arteries may result in absent pulses or unreliable monitoring on the shunt
side. Invasive arterial access should be planned for the opposite side or in the lower limbs if bilateral BT shunts have been placed.
• Prior coarctation repair – any residual aortic coarctation may result in upper extremity (UE) hypertension and lower extremity (LE) hypotension. Both UE and LE should be monitored to assess perfusion.
• Prior need for peripheral or central cannulation – as noted earlier, peripheral venous and arterial vessel patency should be assessed. If placement of a bicaval dual lumen catheter into the internal jugular vein is required for central venovenous ECMO, the anatomy and patency of this vessel should also be established.
What Perioperative Hemodynamic Goals Should Be Taken into Consideration when Preparing for Noncardiac Surgery in the Patient with Failing Fontan Physiology?
○ The patient with failing Fontan physiology requires careful consideration of choice of anesthetic technique including local, regional, neuraxial, or general anesthesia, agents, pressor/inotrope management, and ventilator mode.
○ As high preload is essential for the maintenance of cardiac output in the failing Fontan patient, spontaneous ventilation is preferred as positive pressure ventilation may dramatically decrease preload.
Are There Any Other Preoperative Considerations Specific to Fontan Patients for Noncardiac Surgery?
• These patients should be scheduled as first case of the day to minimize fluid shifts due to fasting and to ensure that adequate assistance is available if required.
-Chronic medications are usually continued and may include pulmonary vasodilators, endothelin receptor antagonists, and calcium channel blockers. Angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, and diuretics are the exception.
- Anticoagulants and antiplatelet agents should be coordinated by the multidisciplinary team, and bridging is generally required.
• Premedication with benzodiazepines may benefit uncooperative patients, and ketamine may be warranted for those with developmental delay.
• Bubble-free precautions including meticulous line de-airing as well as use of in-line air filters are warranted to avoid paradoxical embolism in the setting of intra-/extracardiac
shunts. Fontan patients with venovenous collaterals are at increased risk of shunting.
• Endocarditis prophylaxis should be considered.
• Transcutaneous defibrillator pads should be applied during the perioperative period and the use of electrocautery discussed with the attending surgeon.
• Both positive pressure ventilation and the institution of pneumoperitoneum during laparoscopy may significantly impair systemic venous return to the Fontan circulation and adversely affect cardiac output.
-Carbon dioxide (CO2) insufflation pressures should be limited to less than 10–12 cmH2O.
-Failing Fontan right to left shunt exacerbation may occur if PVR is increased by the physiologic effects of establishing a pneumoperitonuem. -These include atelectasis secondary to increased intra-abdominal pressure, decreased preload, and hypercarbia secondary to CO2 absorption
What Monitoring Modalities Do You Envisage Using for This Procedure Fontan?
• End-tidal CO2 may not accurately reflect arterial CO2 as intra-/extracardiac shunts reduce pulmonary blood flow and CO2 exchange. For this reason, invasive arterial
monitoring allows for repeated blood sampling.
• Central venous access is indicated for the high-risk patient undergoing major surgery or who may have challenging vascular access. Removal as soon as possible in the post-
operative period will decrease the thrombotic risk.
Anatomical reasons preclude the use of a pulmonary artery catheter in many patients with adult congenital disease.
• Transesophageal echocardiography can be invaluable for perioperative management.
• Cerebral oximetry may indirectly reflect the CO2.
• 4-Band electroencephalography may aid in monitoring depth of anesthesia given the variability of pulmonaryblood flow and alveolar/blood transmission of volatile agents.
Is a Neuraxial Technique Appropriate for This Case? Fontan circulation
○ The successful and safe use of epidural anesthesia has been described for laparoscopic cholecystectomy in patients with severe COPD . However, neuraxial blockade should be avoided or utilized with extreme caution as the failing Fontan
patient may not tolerate the reduction in systemic vascular resistance (SVR) associated with a sympathectomy.
○ If epidural anesthesia is utilized, invasive arterial monitoring is warranted for beat-to-beat blood pressure monitoring as well as to guide intravascular volume administration. Careful titration of the epidural anesthetic is necessary.
The Patient Is Curious About What to Expect in the Early Recovery Period. What Factors Should Be Taken into Consideration When Counseling Him? LAP choline Fontan circulation
• Fontan patients benefit from immediate postoperative extubation, especially if pulmonary hypertension is present.
> Airway reactivity and coughing should be minimized to decrease the sympathetic response to extubation.
• Patients should be carefully monitored in the post-anesthesia care unit. > Even partial airway obstruction with hypoxia and/or hypercarbia may increase PVR.
• Sympathetic stressors such as pain and anxiety should be aggressively managed.
• A period of controlled ventilation in an intensive care unit setting may be warranted.
A 20-year-old man presents for laparoscopic cholecystectomy
for acute cholecystitis. He has a history of tricuspid atresia
(Fig. 3.1) palliated with a right Blalock-Taussig (BT) shunt
at birth (Fig. 3.2), a corrective superior vena cava to right
pulmonary artery anastomosis (bidirectional Glenn shunt)
procedure with ligation of the BT shunt at age 6 months
(Fig. 3.3), and an extracardiac conduit from the inferior
vena cava to right pulmonary artery (Fontan completion) at
age 3 (Fig. 3.4).
In addition to several failed attempts at ablative procedures
for supraventricular tachycardia, this patient has developed
severe atrioventricular valvular regurgitation of the systemic
ventricle and has a residual extracardiac conduit fenestration
with a right to left shunt. He has developed failing Fontan
physiology, with significantly reduced exercise tolerance in
the last 6 months, and was recently listed for cardiac
transplantation when he developed cholecystitis.
Can This Procedure Be Performed on an Ambulatory Basis?
○ Young patients with Fontan physiology may undergo minor surgical procedures on an outpatient basis with appropriate preoperative workup.
○ Minimum discharge criteria have been outlined in Table 3.2 [12].
○ This patient has a right to left intracardiac shunt through a fenestration in the extracardiac conduit, resulting in cyanosis.
○ Paradoxical embolism may occur aggressive de-airing of all lines is essential, and air filters should be considered.
○ In addition, it is critical to maintain systemic vascular resistance (SVR) while avoiding to increase PVR.
○ This includes avoiding hypoxia, hypercarbia, metabolic acidosis, hypothermia, and sympathetic surges.
○ The choice and dose of induction and maintenance agents should minimize reductions in SVR.
○ Both central venous and arterial invasive monitoring will likely be required to maintain the balance between SVR and PVR.
○ The use of vasopressin versus phenylephrine to maintain SVR offers the advantage of avoiding a concomitant rise in PVR.
○ The clinical indicators of failing Fontan physiology in this particular patient warrant postoperative in-patient monitoring
True/False Questions
Which of the following is not considered a high-risk congenital cardiac lesion in a patient coming for a non-cardiac surgical procedure?
(a) Systemic ventricular function of less than 35%.
(b) Pulmonary hypertension.
(c) Intracardiac shunt.
(d) Cyanotic disease.
(e) Severe left-sided obstructive lesion.
C
True/False Questions
2. Which of the following is not a palliation treatment
method for congenital heart disease?
(a) Blalock-Taussig shunt.
(b) Glenn shunt.
(c) Pulmonary artery banding.
(d) Norwood procedure.
(e) Closure of atrial septal defect.
E?
What Complications Is the Patient with Cardiac Failure Subject to in the Perioperative Period?
> Postoperatively, patients with heart failure are subject to myocardial ischemia and infarction, atrial fibrillation and ventricular arrhythmias, pulmonary congestion leading to hypoxemia, thromboembolic stroke, and hepatic congestion and dysfunction.
A large retrospective multicenter cohort study from 2019 found that patients with heart failure undergoing elective noncardiac surgery had a significantly higher 90-day mortality compared to those without heart failure (crude mortality rate 5.49% compared with 1.22%) [1]. The risk increased
progressively with decreasing systolic function.
How Is Cardiac Failure Classified?
> There is no universally accepted method for classification of heart failure.
The NYHA Functional Classification of the stages of heart failure according to symptomology is often utilized:
• Class I: No symptoms and no limitation of ordinary physical activity
• Class II: Mild symptoms, e.g., mild dyspnea or angina and slight limitation of ordinary activity
• Class III: Marked limitation of physical activity due to symptoms even during less than ordinary activity and comfortable at rest
• Class IV: Severe limitation and marked symptoms of heart failure at rest
The American College of Cardiology (ACC) and the American Heart Association (AHA) classify heart failure according to disease progression [3]:
• Stage A: Patients at risk of developing heart failure but without structural changes or symptoms of heart failure
• Stage B: Structural heart disease but no symptoms or signs of heart failure
• Stage C: Structural heart disease with current or prior symptomatic heart failure
• Stage D: Advanced heart failure and marked symptoms despite maximal medical therapy
In Which Patient Populations Should We Maintain a High Index of Suspicion for the Presence of Cardiac Failure?
○ The commonest underlying causes of cardiac failure include hypertension; coronary artery disease; valvular disease, e.g., aortic stenosis and mitral regurgitation; atrial fibrillation; and dilated cardiomyopathy.
What Are Prognostic Indicators in the Heart Failure Patient Presenting for Elective Surgery?
We will address the following prognostic indicators in the next several questions:
• Is the patient symptomatic?
• Is cardiac failure compensated or decompensated?
• Is left ventricular dysfunction systolic or diastolic (preserved EF)?
• What is the plasma level of B-type natriuretic peptide (BNP) or the inactive N-terminal fragment NT-proBNP?
What Is the Prognostic Significance of Whether the Patient Is Symptomatic or Not? CCF
> Symptomatic heart failure is a known risk factor for postoperative cardiac complications.
Less is known about asymptomatic heart failure.
A single-center prospective cohort study reported the 30-day cardiovascular event rate for elective vascular surgery to be 49% in patients with symptomatic heart failure, 23% with asymptomatic systolic LV dysfunction, 18% with asymptomatic diastolic dysfunction, and 10% with normal LV function
While symptomatic heart failure patients have worse outcomes, this study
demonstrated that asymptomatic left ventricular dysfunction more than doubled the risk of 30-day cardiovascular morbidity compared to those with normal left ventricular ejection fractions.
A more recent large retrospective study of heart failure patients undergoing elective surgery found crude mortality rates at 90 days of 10.1% and 4.8% for symptomatic and asymptomatic heart failure, respectively
How Is Acute Decompensated Heart Failure Recognized?
> Acute decompensated heart failure (ADHF) is a gradual or sudden worsening of the symptoms and signs of heart failure.
It is most often due to a deterioration in chronic heart failure (70% ADHF presentations).
However, up to 20% of patients hospitalized with ADHF are presenting with heart failure for the first time.
Clinical findings are related to pulmonary and systemic congestion.
- Clinical manifestations of ADHF range from mild, e.g., progressive dyspnea, ankle swelling, abdominal distension, or tenderness (secondary to hepatic
congestion), to severe pulmonary edema and cardiogenic shock.
- ADHF may be precipitated by myocardial infarction or ischemia, arrhythmias, uncontrolled hypertension, non-compliance with medications, and infective exacerbations of COPD. No known precipitating factor has been identified in up to 50% of ADHF episodes [9].
- There is a high prevalence of atrial fibrillation, valvular disease, and dilated
cardiomyopathy in patients presenting with ADHF, which is commensurate with the chronic nature of their underlying heart failure.
- Patients presenting for surgery with ADHF should have the procedure postponed in all cases except when lifesaving surgery is necessary.
What Is Heart Failure with Preserved Ejection Fraction?
> Previously termed diastolic dysfunction, the prevalence of heart failure with preserved ejection fraction (HFpEF) is increasing such that approximately half of hospital admissions for heart failure have preserved LVEF.
HFpEF patients are more likely to be female, hypertensive, and of advanced age.
Other associated conditions include obesity, obstructive sleep apnea, and lung disease
Not all patients with echocardiographic evidence of diastolic dysfunction and preserved EF have HFpEF.
The clinical constellation of heart failure symptoms and signs must accompany these findings to make such a diagnosis
Echocardiographic findings typically seen with HFpEF include LV hypertrophy and left atrial enlargement.
Definitive diagnosis is made during cardiac catheterization on demonstration of elevated LV filling pressures with EF ≥50% [12].
Heart failure with reduced ejection fraction (HFrEF), previously known as systolic heart failure, is typically associated with ischemic heart disease and valvular heart disease.
- Patients typically have increased left ventricular volume and reduced ejection fraction.
No specific treatment has been shown to improve survival in patients with HFpEF.
The foundations of treatment are based on optimal management of hypertension, use of diuretics to relieve symptoms associated with congestion, and treatment of associated conditions, e.g., atrial fibrillation.
Amyloid cardiomyopathy is becoming increasingly recognized as an etiological factor in HFpEF [13].
Screening for cardiac amyloidosis should be considered in at-risk patients (see Chap. 49 for a more detailed discussion on cardiac disease associated with amyloidosis).
How Should the Patient with Cardiac Failure Be Evaluated Preoperatively?
- Clinical evaluation of severity of symptoms and stability of disease can be performed in the office.
- Functional capacity can be determined using the metabolic equivalent score or Duke Activity Status Index (see Chap. 2).
- Symptoms and signs of heart failure which can be used to ascertain severity are outlined in Table 5.1.
- As we have seen above, lack of symptoms does not mean that risk is negligible.
- As outlined in Chap. 2, the Revised Cardiac Risk Index and NSQIP
Surgical Risk Calculator are useful tools for evaluating perioperative risk [14, 15]. - ECG may provide important information relating to the etiology of heart failure, e.g., prior myocardial infarction, atrial fibrillation, and LV hypertrophy associated with hypertension.
- A diagnosis of chronic heart failure due to LV systolic dysfunction is unlikely in the presence of a normal ECG or one that shows only minor abnormalities [16].
- CXR findings that help to differentiate heart failure from pulmonary causes of dyspnea include the presence of cardiomegaly, alveolar pulmonary edema (initially seen as perihilar batwing opacities but becoming more generalized
over time), Kerley B lines of interstitial edema, prominence of the upper zone vessels, and pleural effusions. However, in the setting of optimization for elective surgery, a change or new findings on CXR would likely correlate with a clinical picture indicating acute decompensation, in which case
surgery will almost certainly become deprioritized. - Brain natriuretic peptide (BNP) and N-terminal fragment of proBNP (NT-proBNP) are cardiac biomarkers released from the myocardium in response to stimuli such as ischemia or cardiomyocyte stretch. BNP is synthesized as a prehormone, proBNP, which upon release into the
circulation is cleaved into the biologically active BNP and an inactive N-terminal fragment NT-proBNP [17]. - These biomarkers have excellent sensitivity but limited specificity for diagnosing heart failure. Moreover, BNP level may be proportionate to the risk. This is especially relevant for the perioperative physician. Much of the literature pertaining to BNP and cardiac failure concerns the acute phase of the condition.
- With this in mind, a systematic review of 19 studies where plasma BNP from patients at all stages of the disease was used to determine the relative risk of cardiac events or death reported that every 100 pg/ml increase was
associated with a 35% increase in the relative risk of death
[18]. - There is ample evidence that persistently elevated plasma BNP, despite optimal medical treatment, is a poor prognosticator [19, 20].
- Echocardiography can provide useful information regarding cardiac function and structure. A reduced EF is an independent predictor of mortality in heart failure patients [21].
- However, a normal ejection does not rule out heart failure, considering that approximately half of hospital admissions for heart failure have preserved EF. Echocardiographic demonstration of preserved EF with concomitant structural abnormalities, e.g., LV hypertrophy or left atrial enlargement, is required, along with clinical findings, to confirm the presence of HFpEF.
- Echocardiography is also useful for evaluation of valvular dysfunction, right ventricular function, and pulmonary artery pressure all prognostic indicators in heart failure [22].
- Though LVEF is an established prognostic indicator in cardiac failure, BNP measurement may be more accessible.
- Preoperative NT-proBNP has been shown to be more predictive of major perioperative cardiac complications compared to echocardiography [23]. The Canadian Cardiovascular Society (CCS) recommends measuring NT-proBNP or BNP before noncardiac surgery in patients over 65 years or those
between 45 and 64 years who have a Revised Cardiac Risk Index (RCRI) score of ≥1 (Table 5.2) [24]. CCS also recommends against obtaining a resting echocardiogram preoperatively to enhance cardiac risk estimation unless clinical examination suggests an undiagnosed, severe obstructive
abnormality, e.g., aortic stenosi
What Are the Goals of Optimization for heart failure?
• Identify patients with asymptomatic heart failure.
• Identify and minimize symptoms, especially those related to pulmonary congestion and low output failure.
• Identify and treat precipitating factors, e.g., ischemia, hypertension, arrhythmia, and valvular disease.
• Enhance end-organ perfusion and oxygenation.
What Medical Therapy Is Used to Optimize the Heart Failure Patient?
- Angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARBs) are first-line therapies for the patient with heart failure with reduced EF. ARBs are used in patients intolerant to ACEi.
- These medications should be withheld on the day of surgery to minimize excessive intraoperative hypotension.
- Based on more recent data, a combination of a neprilysin inhibitor and ARB, angiotensin receptor blocker-neprilysin inhibitor (ARNI), sacubitril/valsartan, may be substituted for ACEi or ARB single therapy when the following conditions are met:
• LVEF <40%, BNP or NT-proBNP has been elevated or the patient has been hospitalized for the treatment of heart failure in the past year, and serum potassium <5.2 mmol/L. Neprilysin inhibition decreases the degradation of atrial and brain natriuretic peptide and bradykinin – peptides that evoke
vasodilation, natriuresis, and diuresis.
• Specific beta-blockers for heart failure management are bisoprolol, extended-release metoprolol, and carvedilol.
These specific beta-blockers have been shown to reduce mortality, hospitalization rate, and symptoms in patients with reduced LVEF Beta-blockers should be continued in patients already taking them but should not be started for the first time in the preoperative period.
• Aldosterone receptor antagonists, e.g., spironolactone, reduce mortality in patients with LVEF <35% and NYHA Class II–IV heart failure. Careful monitoring of serum potassium and renal function is required as there is a risk of life-threatening hyperkalemia and renal insufficiency.
• Diuretics are used for symptomatic relief of fluid retention. Patients taking diuretic therapy are at increased risk for perioperative hypovolemia and hypokalemia. This warrants a preoperative electrolyte screen.
• Digoxin can be beneficial in patients with heart failure with reduced EF who are on optimal evidence-based medical therapy (ACEi or ARB or ARNI and beta-blocker and aldo-sterone receptor antagonist) but remain symptomatic.
What Is the Role of Implantable Cardioverter-Defibrillators and Permanent Pacemakers in the Heart Failure Patient?
○ Patients with LV dysfunction are at risk of sudden cardiac death secondary to ventricular arrhythmias.
○ This risk increases as LVEF decreases.
○ Implantable cardioverter-defibrillator (ICD) devices reduce mortality through prevention of sudden cardiac death in certain patients: those with
LVEF of ≤35%, at least 40 days post myocardial infarction, NYHA Class II or III symptoms, on long-term guideline~directed medical therapy, and expected to live for 1 year or longer.
○ ICD devices can also act as pacemakers.
○ Cardiac resynchronization therapy (CRT) may be useful in certain heart failure patients, e.g., those with reduced EF (≤35%), who are in sinus rhythm with a QRS duration of ≥150 ms.
○ Specific indications and contraindications for CRT in heart failure are detailed in the 2013 ACCF/AHA Heart Failure Guidelines [3].
How Is the Severity of AS Categorized?
- AS is classified as mild, moderate, or severe.
- Aortic valve area, mean and peak pressure gradient across the aortic valve, as well as jet velocity can be used to assess severity.
- Patients with a low ejection fraction and severe AS will have a small transvalvular pressure gradient and subsequently are at risk for underestimation of disease severity
Which Patients with AS Are Considered
Candidates for Surgical Repair/
Replacement?
- The need for aortic valve replacement (AVR) is determined by taking account of (1) whether the patient is symptomatic, (2) severity of disease, and (3) left ventricular ejection fraction (LVEF).
- Surgery should be offered to patients with symptomatic severe AS (mean pressure gradient >40 mm Hg).
- Patients with asymptomatic severe AS with LVEF <50% or having other cardiac surgery should also be offered AVR surgery.
- Patients with asymptomatic severe AS and an abnormal exercise tolerance test are reasonable candidates for surgery.
- Patients with moderate AS (mean pressure gradient 20–39 mm Hg) who are asymptomatic are considered surgical candidates only if having other cardiac surgery.
- Patients with moderate AS who are symptomatic are considered for surgery if LVEF <50% and/or valve area is <1 cm2.
- Patients may proceed to transcatheter aortic valve implantation if suitable, rather than open surgery requiring cardiopulmonary bypass.
What Are the Reasons for Not Replacing a Severely Stenotic Valve Prior to Noncardiac Surgery?
• Very short life expectancy
• Lack of symptoms related to AS and patient aware and willing to accept the increased perioperative risk
• Emergency noncardiac surgery or cancer surgery
• Patient refusal of AVR procedure
What Is the Definition of PAH?
○ PAH is said to be present when PAPm is ≥25 mmHg at rest when measured directly via right heart catheterization [2].
○ The upper resting value for normal PAPm is 20 mmHg (usual range 9–18 mmHg).
○ PAPm is calculated by using the following equation
How Should “Elevated” PAP Reported in a Routine Echocardiogram Be Interpreted?
○ Echocardiography is a vital noninvasive screening and diagnostic tool in the assessment of cardiac function and hemodynamics.
○ As part of a complete echocardiographic examination, estimated PAP values (using validated formulas) are reported if the quality of the study and appropriate Doppler-/2D-derived data can be obtained.
○ While the sensitivity of Doppler echocardiography in estimating PAP is
adequate, specificity/accuracy is relatively low when compared to direct measurement during right heart cathe-terization [3]. This is particularly true in the presence of severe tricuspid regurgitation where there is a very high
likelihood (>50%) of overestimating PAPm [4].
○ In interpreting Doppler-derived elevated values of PAP, clinical correlates and other 2D echocardiographic findings suggestive of RV chronic pressure overload (dilated/rounded right atrium (RA), PA enlargement, RV dilatation/dysfunction, and D-shaped LV) should be sought to support a potential diagnosis of PAH.
○ It is generally agreed that echocardiographic-derived estimated PAPs values of <40 mmHg, in the absence of any other clinical or echocardiographic findings suggestive of PAH, are reassuring and in most cases obviate the need for invasive right heart catheterization.
What Are the Clinical Manifestations of MFS?
○ MFS is a multisystem disorder with abnormalities mainly involving the skeletal, cardiovascular, ocular, and pulmonary systems in addition to the skin and dura.
○ A set of defined diagnostic criteria, known as the Ghent nosology, comprising major and minor manifestations, has been developed to aid recognition and diagnosis.
○ Aortic root dilatation/dissection and ocular lens dislocation (ectopia lentis) are the cardinal clinical features.
○ The revised Ghent criteria are summarized in Tables 12.2 and 12.3.
