Cardiovascular

Hemodynamics, ischemia, arrhythmia, valvular disease and antihypertensives — the single densest organ-system block.

Exam weight 8–10% · 3 QBank items · 5 flashcards

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Cardiac physiology

Cardiac output = stroke volume × heart rate; at high heart rates diastolic filling time falls and CO drops.
Preload correlates with ventricular end-diastolic volume; afterload with mean arterial pressure and wall stress (Laplace).
Ejection fraction = SV/EDV; reduced in systolic failure, preserved in diastolic dysfunction.
S3 signals volume overload (dilated ventricle); S4 signals a stiff ventricle (hypertrophy or ischemia).

Stable angina is demand ischemia relieved by rest; unstable angina is plaque rupture at rest with normal troponin.
Troponin rises at 3–6 hours, peaks at 24 hours, stays elevated 7–10 days; CK-MB is used to detect reinfarction.
ST elevation localisation: II/III/aVF inferior (RCA), V1–V4 anteroseptal (LAD), I/aVL/V5–V6 lateral (circumflex).
Post-MI complications by timing: arrhythmia in the first day, free-wall rupture and papillary muscle rupture at 3–14 days, Dressler syndrome at weeks.

Aortic stenosis: crescendo-decrescendo systolic murmur radiating to carotids, pulsus parvus et tardus, syncope on exertion.
Mitral regurgitation: holosystolic murmur radiating to the axilla, increases with handgrip.
Hypertrophic cardiomyopathy murmur increases with Valsalva and standing (decreased preload) — opposite of most murmurs.
Mitral valve prolapse: mid-systolic click; myxomatous degeneration, associated with Marfan and Ehlers-Danlos.

Atrial fibrillation: irregularly irregular with no P waves; anticoagulate based on CHA₂DS₂-VASc.
Mobitz I (Wenckebach) progressively lengthens PR then drops a beat and is usually benign; Mobitz II drops without warning and needs a pacemaker.
Wolff-Parkinson-White: short PR with a delta wave; avoid AV nodal blockers in pre-excited atrial fibrillation.
Torsades de pointes on a long QT — give IV magnesium and remove offending drugs.

ACE inhibitors cause dry cough (bradykinin), hyperkalemia and angioedema; contraindicated in bilateral renal artery stenosis and pregnancy.
Dihydropyridine calcium blockers cause peripheral edema and reflex tachycardia; verapamil/diltiazem depress the AV node and cause constipation.
Statins can cause myopathy and transaminitis; risk rises with fibrates and CYP3A4 inhibitors.
Nitrates reduce preload; contraindicated within 24–48 hours of PDE-5 inhibitors.