Dr. Usman's Cardiology Notes

  Congenital AV Block – Pacing Indications Congenital atrioventricular (AV) block may be isolated (often immune-mediated due to maternal anti-Ro/SSA or anti-La antibodies) or associated with structural heart disease (e.g., congenitally corrected TGA). Pacing decisions depend on symptoms, ventricular rate, ventricular function, and risk markers. --- 1. Class I Indications (Permanent Pacemaker Recommended) 1. Symptomatic bradycardia Syncope, presyncope Heart failure Exercise intolerance 2. Asymptomatic complete (3rd-degree) AV block with: Wide QRS escape rhythm Ventricular dysfunction Complex ventricular ectopy Prolonged QT interval 3. Neonates/Infants with complete AV block and: Ventricular rate <55 bpm Ventricular rate <70 bpm if associated with congenital heart disease 4. Postoperative advanced AV block Persisting >7–10 days after congenital cardiac surgery --- 2. Class IIa Indications (Reasonable to Pace) 1. Asymptomatic complete AV block beyond infancy with: Average hea...

Vericiguat in Heart Failure: Mechanism, Evidence, Dosing, and Clinical Positiom Introduction Vericiguat is a novel oral soluble guanylate cyclase (sGC) stimulator approved for patients with symptomatic chronic heart failure with reduced ejection fraction (HFrEF) who have had recent worsening heart failure despite guideline-directed medical therapy (GDMT). It targets the nitric oxide–sGC–cyclic GMP pathway, which is impaired in advanced heart failure. This article provides a clinically focused, guideline-oriented review of vericiguat for practicing physicians and cardiology trainees. --- Pathophysiologic Rationale In chronic HFrEF: Endothelial dysfunction reduces nitric oxide (NO) bioavailability Oxidative stress impairs soluble guanylate cyclase activity Reduced cyclic GMP (cGMP) leads to: Increased vascular tone Myocardial stiffness Fibrosis Progressive ventricular remodeling Vericiguat directly stimulates soluble guanylate cyclase and enhances its sensitivity to endogenous NO, restor...

Comparative Pharmacology of NOACs (DOACs) Non–vitamin K oral anticoagulants (NOACs), also called direct oral anticoagulants (DOACs), include: Dabigatran Rivaroxaban Apixaban Edoxaban They differ in mechanism, pharmacokinetics, renal dependence, drug interactions, and reversal strategies. --- 1. Mechanism of Action Drug Target Site in Coagulation Cascade Dabigatran Direct Thrombin (Factor IIa) inhibitor Final step – prevents fibrin formation Rivaroxaban Direct Factor Xa inhibitor Blocks conversion of prothrombin → thrombin Apixaban Direct Factor Xa inhibitor Same Edoxaban Direct Factor Xa inhibitor Same Key distinction: Dabigatran → Thrombin inhibitor Others → Factor Xa inhibitors --- 2. Pharmacokinetics Comparison Parameter Dabigatran Rivaroxaban Apixaban Edoxaban Bioavailability 6–7% 80–100% (10 mg) ~50% ~62% Tmax 1–3 h 2–4 h 3–4 h 1–2 h Half-life 12–17 h 5–13 h 8–15 h 10–14 h Dosing BID OD (or BID ACS) BID OD Food effect No major Required for 15/20 mg No No Clinical pearl: Rivaroxaba...

ECG Findings of Pulmonary Embolism (PE) 1. Sinus Tachycardia (Most Common Finding) • Most frequent ECG abnormality in acute PE • Heart rate usually >100 bpm • Reflects hypoxia, pain, anxiety, and sympathetic activation --- 2. S1Q3T3 Pattern (McGinn–White Sign) • Deep S wave in Lead I • Q wave in Lead III • T-wave inversion in Lead III • Suggests acute right heart strain • Seen in <20% cases (not sensitive but classic for exams) --- 3. Right Heart Strain Pattern • T-wave inversion in V1–V4 • T-wave inversion in inferior leads (II, III, aVF) • Reflects acute RV pressure overload • Associated with worse prognosis --- 4. Right Bundle Branch Block (RBBB) • Incomplete or complete RBBB • rSR′ pattern in V1 • Wide QRS if complete (>120 ms) • Caused by acute RV dilation --- 5. Right Axis Deviation • QRS axis > +90° • Dominant R wave in lead III • Reflects RV strain --- 6. P Pulmonale (Right Atrial Enlargement) • Tall peaked P wave (>2.5 mm) in lead II • Indicates acute right atri...

Narrow QRS Tachycardia: Differential Diagnosis  Narrow QRS Tachycardia: Differential Diagnosis Comprehensive Clinical & ECG-Based Approach Introduction Narrow QRS tachycardia is one of the most frequently encountered arrhythmias in emergency rooms, CCUs, and electrophysiology labs. A narrow complex (QRS < 120 ms) indicates that ventricular activation is occurring through the normal His–Purkinje system. Therefore, the arrhythmia origin is either: • Supraventricular (atria or AV junction) • Ventricular but conducting normally via the conduction system (rare) Correct diagnosis is critical because management differs dramatically between sinus tachycardia, atrial tachyarrhythmias, and AV reentrant tachycardias. --- Definition Narrow QRS Tachycardia = Heart rate >100 bpm QRS duration <120 ms --- Stepwise Clinical Approach Before jumping to labels, always analyze systematically: 1. Is it regular or irregular? 2. Are P waves visible? 3. What is the RP interval? 4. Is there AV ...

NOACs Dosing and Reversal A Practical, Guideline-Based Clinical Guide Introduction Non–vitamin K oral anticoagulants (NOACs), also called direct oral anticoagulants (DOACs), have largely replaced warfarin in many clinical settings due to predictable pharmacokinetics, fewer interactions, and no routine INR monitoring requirement. Commonly used NOACs include: Dabigatran Rivaroxaban Apixaban Edoxaban --- Mechanism of Action Drug Target Dabigatran Direct thrombin (Factor IIa) inhibitor Rivaroxaban Factor Xa inhibitor Apixaban Factor Xa inhibitor Edoxaban Factor Xa inhibitor --- Indications 1. Non-valvular atrial fibrillation (stroke prevention) 2. Treatment of DVT 3. Treatment of PE 4. Secondary prevention of VTE 5. Post-orthopedic surgery thromboprophylaxis --- Standard Dosing 1. Stroke Prevention in Atrial Fibrillation Dabigatran 150 mg twice daily 110 mg twice daily (elderly/high bleeding risk) Rivaroxaban 20 mg once daily (with food) 15 mg once daily if CrCl 15–49 mL/min Apixaban 5 mg ...

Carotid Sinus Hypersensitivity (CSH) Definition Carotid sinus hypersensitivity (CSH) is an exaggerated response to carotid sinus stimulation leading to: • Excessive bradycardia (cardioinhibitory response) • Hypotension (vasodepressor response) • Or a combination of both It is an important cause of unexplained syncope, especially in elderly patients. --- Anatomy and Physiology of the Carotid Sinus • Located at the bifurcation of the common carotid artery • Contains baroreceptors sensitive to stretch • Afferent pathway: Glossopharyngeal nerve (Hering’s nerve) • Central integration: Medulla • Efferent pathway: Vagus nerve → SA/AV node Normal function: Maintains blood pressure homeostasis In CSH: Minor stimulation → exaggerated reflex --- Epidemiology • More common in age > 60 years • Male predominance • Frequently associated with hypertension • Seen in patients with recurrent unexplained falls CSH may be present in asymptomatic elderly individuals, so clinical correlation is essential....