Flashcards in cardio pathophys Deck (390)
Wall stress = ((pressure x chamber radius)/2x wall thickness)
What factors increase cardiac contractility?
Increased SS tone
What factors decrease contractility?
SS blockade (Beta Blocker)
What is concentric hypertrophy?
Seen w/ high BP
increase in number of sarcomeres laid in parallel -> decreased cavity size and increased wall thickness -> decreased wall stress w/ preserved contractility
What is eccentric hypertrophy?
Occurs w/ chronically elevated preload
Increased sarcomeres in series -> increased chamber size + increased wall stress -> increased sarcomeres in parallel
proportional increases in cavity size and wall thickness
What is concentric remodelling?
Reversible, physiologic LV hypertrophy seen in athletes.
4 ways that IC Ca++ is recovered after cardiomyocyte contraction
1: SERCA - in SR, ATP dependent
2: Na/Ca exchanger - uses Na gradient to move Ca out
3: Plasma membrane Ca++ -ATPase
4: Mitochondrial Ca++ uniporter
What is preload?
Passive tension in cardiac myocyte at rest - length of cell prior to contraction
Greater length -> stronger contraction
What is afterload?
The force that a muscle cell must overcome in order to contract
What is isometric contraction?
Afterload > contraction force
sarcomere does not shorten
What is contractility?
contractility = inotropy
intrinsic ability of cardiac myocyte to alter ability to contract independent of preload and afterload
due to changes in biochemical environment of myocyte
due to increased actin-myosin interractions.
EDV - ESV = SV
EF = SV / EDV
3 phases of ventricular filling
Early rapid filling
Slow mid-diastolic filling
Rapid filling from atrial contraction
2 factors that influence Preload
Venous return (blood volume, venous tone, posture, pericardial constraint, atrial contraction efficacy)
What is normal EF? What EF %s indicate mild, moderate, severe dysfunction?
Mild LV dysfunction: 45-54%
Moderate LV dysfunction: 30-44%
Severe LV dysfunction: <30%
2 methods of measuring CO
Thermodilution: most common - cath inserted, cold saline injected in RA, measured in PA, CO is calculated
Fick method: tedious
equation: CO = O2 consumption / AV O2 difference
What is a Wood Unit (WU)?
Used in calculations of TPR
WU = (dyne . sec . cm^-5) / 80
How is TPR calculated? Normal values?
measure of afterload
Mean pressure difference across vascular bed / mean blood flow
Systemic VR = (MAP - MRAP)/CO. Normal = 13-16 WU
Pulmonary VR = (MPAP - PCWP)/CO. Normal = 0.5-11 WU
What is initial treatment for STEMI?
If not immediately possible - thrombolytics
what anti-ischemic treatments are recommended for early hospital care of ischemic heart disease?
1: oxygen (maintain O2 sat >90%)
2: nitrates (SLx3 or IV for ongoing ischemia, HF, HTN)
3: Oral B-blocker in 1st 24 hrs if no contraindication
4: NDHP Ca++ channel blocker if B-blocker contraindicated
5: ACE inhibitor in 1st 24 hrs for HF or EF <40%
What are contraindications for Nitrate use?
Hypotension (present or likely)
Right ventricular infarct
Severe aortic stenosis
PDEi taken in last 24 hours
What are indications for Beta blocker use in Ischemic heart disease and what are the preferred agents?
Ongoing chest pain, hypertension or tachycardia not caused by HF
Metoprolol or atenolol are preferred
Should a patient w/ MI precipitated by cocaine use be treated with a beta-blocker?
Blockade of B2 mediated vasodilation may precipitate coronary artery spasm
What patients may receive IV beta blocker?
Patients with ischemic heart disease and significant hypertension
Afib with RVR
Contraindications for beta-blocker use
hypotension, bradycardia, heart block, pulmonary edema
MI assoc. w/ cocaine use
What is the recommended statin in treatment of ischemic heart disease?
Atorvastatin, 80mg / day
What studies demonstrated the efficacy of statin treatment in treatment of ischemic heart disease?
PROVEIT-TIMI 22 and MIRACL
What is class III therapy for ischemic heart disease?
-Nitrates if Systolic pressure <90
-Nitrates if Sildenafil or Tadalafil w/in 24 hrs
-Immediate release Ca Channel blockers w/o B-blocker
-IV B-blocker if AHF, low output, long PR, 2nd or 3rd deg heart block, asthma or reactive airway disease
-NSAIDs and COX-2 inhibitors