Dilated Cardiomyopathy Flashcards
(12 cards)
What are the classifications of cardiomyopathies?
Dilated
Hypertrophic
Restrictive
Arrhythmogenic Right Ventricular
Unclassified
They can be genetic or acquired
How is dilated cardiomyopathy defined?
Dilated cardiomyopathy is the presence of left ventricular dilatation and systolic dysfunction in the absence of abnormal loading conditions such as hypertension or valvular disease.
N.B. There may also be similar right sided changes
What are the genetic causes of Dilated cardiomyopathy
Autosomal Dominant defects in cardiac muscle structure
X-linked Dilated Cardiomyopathy
X-linked Muscular dystrophies such as Becker and Duchennes
What are the acquired causes of dilated cardiomyopathy
Viral Myocarditis
Drugs e.g. chemotherapy agents
Alcohol
Tachycardiomyopathy
Pregnancy-Associated Dilated Cardiomyopathy
Nutrional Defects e.g. thiamine
Briefly explain the pathophysiology of dilated cardiomyopathy
As the left ventricle enlarges
The overlap between actin and myosin filaments reduces
Resulting in a reduction in stroke volume
The stretch also results in valvular dysfunction
According to Laplace’s law the increased fluid content of the ventricle increases wall tension, which impairs oxygen delivery and causes further cardiac muscle compromise and loss of function.
The inefficiency in systole also results in the development of intracardiac thrombus
What are the possible ways in which a patient with dilated cardiomyopathy may present?
Signs and symptoms of heart failure i.e:
Shortness of Breath, Poor Exercise Tolerance, Fatigue, Ascites,
Peripheral Oedema
Arrhythmias (and their consequences)
Embolic Events
Sudden Death
Screening (of family members after diagnosis of an index case)
What are the pharmacological management options for a patient with dilated cardiomyopathy
Betablockers
Aldosterone Inhibitors
Diuretics
ACE inhibitors / Angiotensin 2 receptor blockers
Anticoagulants
SGLT2 inhibitors, aka the Gliflozins (the mechanism is unclear, but while they are predominantly used for the treatment of diabetes, they do reduce cardiovascular events and hospitalisations for heart failure)
Atrial Natriuretic Peptide (IV use only)
Angiotensin Receptor Neprilysin inhibitor (ANRi)
Neprilysin breaks down endogenous peptides such as atrial natriuretic peptide, and so inhibition of this promotes favorable effects in Dilated Cardiomyopathy.
However, neprilysin also breaks down angiotensin 2, and inhibition of this effect would lead to vasoconstriction, which is unhelpful in the setting of Dilated Cardiomyopathy. Hence, the neprilysin inhibitor is given in conjunction with an angiotensin-2 receptor blocker
What are the Non-pharmacological management options for a patient with dilated cardiomyopathy
Partial Left Ventriculectomy (an operation which aims to reduce the size of a part of the heart [in this case, the left ventricle] so it can pump blood more efficiently)
Cardiac Resynchronisation pacing therapy
Implantable Cardiac Defibrilator
Left Ventricular Assist device (as a bridge to transplant)
Heart Transplant
What are the predictors of poor outcome in patients with dilated cardiomyopathy undergoing surgery
Left Ventricular Ejection Fraction of <20%
Elevated Left Ventricular End Diastolic Pressure
Left Ventricular Hypokinesia
Non-Sustained Ventricular Tachycardia
What haemodynamic goals should one aim for when anaesthetising a patient with Dilated Cardiomyopathy
Avoiding Myocardial Depression
Maintaining adequate preload
Preventing increases in afterload
Avoid Tachycardia and Tachyarrhythmia
Prevent sudden hypotension (as this will impair coronary perfusion)
NB the heart is struggling, don’t do anything that makes it more difficult to eject blood
What anaesthetic approaches are there to achieve the desired haemodynamic goals in Dilated Cardiomyopathy patients
Perform surgery under a peripheral nerve block once (if feasible, this will have minimal effect on haemodynamics)
Use of central neuraxial block (as a reduction in afterload can improve cardiac output, although you can overdo it, and too much of a drop will result in myocardial hypoperfusion)
Slow IV induction (as circulation time will be impaired) can help avoid the overdosing of agents and hence prevent an excessive decrease in afterload and myocardial depression
Increased opioid component to IV anaesthetic technique as these have less of an impact on haemodynamics and will reduce the need for other anaesthetic agents
Balance maintenance of anaesthesia as inhalation agents cause myocardial depression in high concentrations
What monitoring techniques (beyond the standard basic monitoring requirements for anaesthesia) and the information that may be gained from them, that may help guide anaesthesia management to achieve the desired haemodynamic goals.
Transoesophageal Echocardiography to provide a dynamic assessment of heart filling and cardiac output
Oesophageal Doppler to provide an algorithm-based assessment of stroke volume
Central Venous Catheterisation for assessment of cardiac preload
Invasive Arterial Blood Pressure Monitoring to give an algorithm-based assessment of stroke volume variation, assessment of acid-base, gas exchange, and electrolyte status, all of which could have a deleterious impact on heart function,n and beat-to-beat blood pressure monitoring to assist in rapid response to adverse changes
Depth of anesthesia monitoring to give an indication of anaesthetic depth and hence allow the minimum necessary anaesthetic drug administration
Cerebral Oxygenatin monitoring to assess O2 delivery and allow appropriate manipulation to reduce the risk of postoperative cognitive dysfunction
