Dr. Usman's Cardiology Notes

  Criteria of Culprit Artery in Inferior Wall STEMI Identifying the culprit artery (RCA vs LCX) in inferior wall STEMI from surface ECG helps anticipate complications, guide cath strategy, and assess myocardial area at risk. This post summarizes ECG-based criteria commonly used to differentiate RCA from LCX occlusion. ST Elevation in Leads III and II Key principle: Lead III reflects RCA territory more strongly than lead II Findings favoring RCA occlusion ST elevation in lead III > lead II ST depression in aVL greater than lead I These patterns indicate an injury vector directed inferiorly and rightward, consistent with RCA involvement. --- Role of Lateral Precordial Leads (V5–V6) --- V5 and V6 have limited value in differentiating RCA from LCX occlusion Presence of ST elevation in V5–V6 suggests: Larger myocardial area at risk Possible extension beyond isolated inferior infarction They should be interpreted as markers of infarct size rather than culprit artery. --- ST-Segment Be...

Arterial Pulse Waveforms – Clinical Interpretation and Significance --- Importance of Pulse Waveform Analysis Examination of the arterial pulse is a powerful bedside tool. Beyond rate and rhythm, the contour, amplitude, and timing of the pulse provide clues to underlying valvular disease, cardiomyopathy, and ventricular function. Pulse waveform abnormalities often mirror left ventricular systolic dynamics and arterial compliance. --- Normal Pulse A normal arterial pulse has: Rapid upstroke Smooth systolic peak Gradual downstroke It reflects normal left ventricular ejection, intact aortic valve function, and compliant arterial system. --- Water Hammer Pulse (Collapsing Pulse) Key Features Bounding, forceful pulse Rapid upstroke followed by sudden collapse Wide pulse pressure Mechanism High systolic pressure from increased stroke volume combined with rapid diastolic runoff leads to abrupt arterial collapse. Common Associations Aortic regurgitation High-output states (e.g., anemia, thyrot...

  Diagnostic Algorithm for Narrow Complex Tachycardia (NCT) Narrow complex tachycardia refers to a regular or irregular tachyarrhythmia with QRS duration <120 ms, implying ventricular activation via the normal His–Purkinje system. A systematic ECG-based approach allows rapid and accurate diagnosis at the bedside. Step 1: Confirm It Is a Narrow Complex Tachycardia QRS duration <120 ms Ventricular rate usually >100 bpm If QRS is borderline, consider aberrancy or pre-excited tachycardia separately Step 2: Assess Regularity of RR Interval A. Regular Narrow Complex Tachycardia Common causes: AVNRT AVRT (orthodromic) Atrial tachycardia Atrial flutter with fixed AV conduction (usually 2:1) B. Irregular Narrow Complex Tachycardia Common causes: Atrial fibrillation Atrial flutter with variable AV block Multifocal atrial tachycardia Step 3: Look for P Waves and Their Relationship to QRS Are P waves visible? Clearly visible before QRS → likely atrial ta...

  COMPANION Trial (Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure) Heart failure with reduced ejection fraction (HFrEF) remains a major cause of morbidity and mortality despite advances in pharmacological therapy. Electrical dyssynchrony, reflected by a wide QRS complex, contributes significantly to progressive ventricular dysfunction. The COMPANION trial was a landmark study that established the role of cardiac resynchronization therapy (CRT), with or without a defibrillator, in patients with advanced heart failure. --- Background and Rationale Prior to COMPANION, optimal medical therapy (OMT) was the cornerstone of heart failure management. However, many patients with severe systolic dysfunction and prolonged QRS continued to experience recurrent hospitalizations and high mortality. CRT was developed to correct interventricular and intraventricular dyssynchrony by simultaneous pacing of both ventricles. COMPANION was designed to determine whether addin...

Bundle Branch Block Morphology on ECG Understanding bundle branch block (BBB) patterns on ECG is a core skill for clinicians, residents, and cardiology trainees. BBB alters ventricular depolarization, producing characteristic QRS morphologies that are best appreciated by systematically comparing leads V1 and V6. Once you train your eye, these patterns become instantly recognizable and clinically meaningful. Normal Ventricular Conduction on ECG In normal conduction, electrical impulses travel simultaneously down the right and left bundle branches, leading to near-synchronous activation of both ventricles. In lead V1, the QRS complex is usually predominantly negative, reflecting left ventricular dominance, while in lead V6 there is a tall, narrow R wave representing efficient left ventricular depolarization. The QRS duration remains narrow, typically less than 120 ms, and ST-T segments follow the QRS direction smoothly. These normal patterns form the baseline against which bundle branch ...

  Diastology on echocardiography refers to the assessment of left ventricular (LV) filling, relaxation, compliance, and filling pressures. It is a core component of modern echo practice because many patients with heart failure, hypertension, diabetes, ischemia, or valvular disease have preserved systolic function but significant diastolic dysfunction. --- Why Diastolic Assessment Matters • Explains symptoms in patients with normal ejection fraction • Essential for diagnosing HFpEF • Reflects myocardial ischemia, fibrosis, and hypertrophy earlier than systolic indices • Guides prognosis and management Diastolic dysfunction often precedes systolic dysfunction. --- Physiology of Diastole (Echo Perspective) Diastole has four functional phases: 1. Isovolumic relaxation 2. Early rapid filling 3. Diastasis 4. Atrial contraction Echo parameters are designed to interrogate these phases. --- Core Echocardiographic Parameters in Diastology 1. Mitral Inflow Doppler Measured using pulsed-wave D...

Cardiac output is one of the most powerful bedside concepts in cardiology and critical care. It connects physiology, echocardiography, and real-time clinical decision-making, especially in unstable patients where numbers matter less than trends and response to intervention. Cardiac output is the volume of blood pumped by the heart per minute. It reflects how effectively the heart meets the metabolic demands of the body. In simple terms, it answers a crucial question: is tissue perfusion adequate? The physiological relationship is straightforward. Cardiac Output = Stroke Volume × Heart Rate What makes this concept clinically rich is how stroke volume is derived and how dynamically it changes with preload, afterload, and contractility. Echocardiographic calculation of cardiac output relies on left ventricular outflow tract (LVOT) measurements. The LVOT is treated as a circular conduit through which blood exits the left ventricle. First, the LVOT diameter is measured in the parasternal lo...