Cardiology Syllabus

State the standard ECG paper speed and voltage calibration, and the duration/amplitude of one small box.

Standard speed is $25\ \text{mm/s}$ and calibration $10\ \text{mm/mV}$. One small box (1 mm) = $0.04\ \text{s}$ horizontally and $0.1\ \text{mV}$ vertically; one large box (5 mm) = $0.20\ \text{s}$.

Give the normal durations of the PR interval and the QRS complex.

Normal PR interval: $0.12\text{–}0.20\ \text{s}$ (3–5 small boxes). Normal QRS duration: $< 0.12\ \text{s}$ (less than 3 small boxes).

How do you quickly estimate heart rate from an ECG using large boxes?

$$HR \approx \frac{300}{\text{number of large boxes between two R waves}}$$ (the 300-150-100-75-60-50 rule). Alternatively, $HR = \frac{1500}{\text{small boxes between R waves}}$.

What ECG finding defines first-degree AV block versus complete (third-degree) AV block?

First-degree AV block: prolonged PR interval $> 0.20\ \text{s}$, every P conducts. Third-degree (complete) block: complete AV dissociation—P waves and QRS are independent with no relationship (atrial rate faster than escape ventricular rate).

What is echocardiography and what is its main advantage?

Echocardiography uses ultrasound to image cardiac structure and function in real time. Advantages: non-invasive, no ionizing radiation, portable, assesses chamber size, wall motion, valves, ejection fraction, and (with Doppler) blood flow.

Contrast transthoracic (TTE) with transesophageal (TEE) echocardiography.

TTE: probe on the chest wall, non-invasive, first-line but limited by body habitus/lungs. TEE: probe in the esophagus, semi-invasive, gives superior posterior-structure images (left atrium, appendage, valves, prosthetic valves, endocarditis, aortic dissection).

What does Doppler echocardiography add, and what equation relates pressure gradient to velocity?

Doppler measures blood flow velocity and direction (valve gradients, regurgitation, stenosis). The simplified Bernoulli equation estimates pressure gradient: $$\Delta P = 4v^{2}$$ where $v$ is peak velocity in m/s and $\Delta P$ in mmHg.

What is cardiac catheterization and what is the gold-standard diagnostic use of coronary angiography?

Cardiac catheterization threads a catheter through a peripheral artery/vein into the heart/coronaries. Coronary angiography (injecting contrast) is the gold standard for visualizing coronary artery anatomy and stenoses.

In cardiac catheterization, what is fractional flow reserve (FFR) and its ischemia threshold?

FFR is the ratio of maximal blood flow (pressure) distal to a stenosis versus proximal (normal), measured under hyperemia: $FFR = \frac{P_{distal}}{P_{aorta}}$. A value $\leq 0.80$ indicates a hemodynamically significant lesion warranting revascularization.

Name two access sites for cardiac catheterization and the preferred one.

The radial artery (wrist) and the femoral artery (groin). Radial access is now preferred for coronary procedures due to fewer bleeding/vascular complications and earlier ambulation.

Compare cardiac MRI and cardiac CT in their primary strengths.

Cardiac MRI: gold standard for tissue characterization (fibrosis/scar via late gadolinium enhancement), myocardial viability, and precise volumes/function; no radiation. Cardiac CT (CTA): excellent for coronary anatomy/calcium scoring, fast, but uses radiation and iodinated contrast.

What is a coronary artery calcium (CAC) score used for?

CAC scoring (via CT, Agatston score) quantifies coronary calcification to refine atherosclerotic cardiovascular disease risk. A score of 0 indicates very low risk; higher scores indicate greater plaque burden and event risk.

What is myocardial perfusion imaging (nuclear SPECT/PET) used to assess?

It uses radiotracers with stress and rest imaging to detect reversible ischemia (perfusion defect on stress that normalizes at rest) versus fixed defects (scar/infarct), assessing functional significance of coronary disease and viability.

What are the three main classes of antianginal drugs and their unifying goal?

Nitrates, beta-blockers, and calcium channel blockers. All reduce myocardial oxygen demand (and/or improve supply) to relieve the imbalance between demand and supply that causes angina.

By what mechanism do nitrates (e.g., nitroglycerin) relieve angina?

Nitrates release nitric oxide (NO), which activates guanylate cyclase, raising cGMP and causing vascular smooth muscle relaxation—primarily venodilation, reducing preload and myocardial oxygen demand; also coronary vasodilation.

How do beta-blockers reduce anginal symptoms?

By blocking $\beta_1$ adrenergic receptors, they lower heart rate, contractility, and blood pressure, decreasing myocardial oxygen demand; the slower heart rate also prolongs diastole, improving coronary perfusion.

What are the four pillars (guideline-directed medical therapy) of HFrEF treatment?

1) ARNI (or ACE inhibitor/ARB), 2) Beta-blocker, 3) Mineralocorticoid receptor antagonist (MRA, e.g., spironolactone), and 4) SGLT2 inhibitor. Together they reduce mortality and hospitalization in HFrEF.

What is the mechanism and toxicity concern of digoxin in heart failure?

Digoxin inhibits the $\ce{Na+/K+}$-ATPase, raising intracellular calcium to increase contractility (positive inotrope) and slowing AV conduction. It has a narrow therapeutic index; toxicity is worsened by hypokalemia and causes arrhythmias, nausea, and visual disturbances.

How do loop diuretics like furosemide help heart failure, and what electrolyte must be monitored?

Loop diuretics inhibit the $\ce{Na+/K+/2Cl-}$ cotransporter in the thick ascending limb of Henle, causing potent diuresis that relieves congestion/edema. Potassium must be monitored (risk of hypokalemia).

State the Vaughan-Williams classification of antiarrhythmic drugs.

Class I: sodium channel blockers (Ia, Ib, Ic). Class II: beta-blockers. Class III: potassium channel blockers (prolong repolarization, e.g., amiodarone). Class IV: non-dihydropyridine calcium channel blockers (verapamil, diltiazem).

Which antiarrhythmic is class III but has properties of all four classes, and what are its major toxicities?

Amiodarone. Toxicities include pulmonary fibrosis, thyroid dysfunction (hypo/hyper), hepatotoxicity, corneal deposits, blue-gray skin, and QT prolongation.

What is the first-line drug for terminating acute paroxysmal supraventricular tachycardia (PSVT) and its mechanism?

Adenosine. It transiently activates $A_1$ receptors, hyperpolarizing AV nodal tissue and briefly blocking AV conduction to interrupt the reentry circuit; it has a very short half-life (seconds).

Contrast the mechanisms of warfarin, heparin, and direct oral anticoagulants (DOACs).

Warfarin inhibits vitamin K epoxide reductase, reducing factors II, VII, IX, X. Heparin potentiates antithrombin to inhibit thrombin (IIa) and Xa. DOACs directly inhibit either factor Xa (rivaroxaban, apixaban) or thrombin (dabigatran).

How do aspirin and clopidogrel differ in their antiplatelet mechanisms?

Aspirin irreversibly inhibits cyclooxygenase-1 (COX-1), blocking thromboxane $A_2$ synthesis. Clopidogrel irreversibly blocks the platelet $P2Y_{12}$ ADP receptor, inhibiting ADP-mediated platelet aggregation.

What lab test monitors warfarin therapy and what is a typical target range for most indications?

The INR (International Normalized Ratio), derived from the prothrombin time. The typical therapeutic target is $2.0\text{–}3.0$ (higher, $2.5\text{–}3.5$, for mechanical mitral valves).

What is percutaneous coronary intervention (PCI) and the role of a drug-eluting stent?

PCI uses a catheter with a balloon to dilate a stenosed coronary artery (angioplasty), usually deploying a stent. Drug-eluting stents release antiproliferative agents (e.g., sirolimus, everolimus) to reduce neointimal hyperplasia and in-stent restenosis.

What is the target "door-to-balloon" time for primary PCI in STEMI, and why does it matter?

The target door-to-balloon time is $\leq 90$ minutes. Rapid reperfusion limits infarct size ("time is muscle"), preserving myocardium and improving survival.

What structural heart intervention is TAVR/TAVI and who is it for?

Transcatheter aortic valve replacement/implantation delivers a prosthetic aortic valve via catheter (usually transfemoral) for severe symptomatic aortic stenosis. Originally for high/prohibitive surgical risk, now also for intermediate and low-risk patients.

What does catheter ablation treat and by what mechanism?

Catheter ablation treats arrhythmias (e.g., atrial fibrillation, SVT, flutter, VT) by delivering radiofrequency energy or cryoablation to destroy the abnormal electrical focus or reentry pathway. Pulmonary vein isolation is the cornerstone for atrial fibrillation.

Classify the major cardiovascular risk factors into non-modifiable versus modifiable.

Non-modifiable: age, male sex, family history/genetics, ethnicity. Modifiable: hypertension, dyslipidemia (high LDL), diabetes mellitus, smoking, obesity, physical inactivity, and unhealthy diet. Lifestyle changes plus statins, BP control, and smoking cessation reduce risk.