A 72-year-old woman from Mumbai with a history of hypertension and diabetes mellitus type 2 presents with palpitations and dyspnea on exertion for 3 days. She denies chest pain. Vital signs: BP 146/88 mmHg, HR 118 bpm (irregular), RR 20/min. On auscultation, the apical impulse is irregular and there is no murmur. ECG shows an irregular rhythm with absent P waves, fine undulating baseline, and a ventricular rate of 110–130 bpm. What is the most likely diagnosis?

Explanation

## Diagnosis: Atrial Fibrillation with Rapid Ventricular Response ### ECG Diagnostic Criteria for Atrial Fibrillation | Feature | Atrial Fibrillation | Atrial Flutter | Sinus Tachycardia | MAT | |---|---|---|---|---| | **P waves** | Absent; fibrillatory baseline | Regular sawtooth pattern | Visible, upright | Multiple morphologies | | **Rhythm** | Irregularly irregular | Regular or variable | Regular | Irregular | | **Baseline** | Fine or coarse undulation | Sawtooth | Isoelectric | Isoelectric | | **Ventricular rate** | Variable (60–160 bpm) | 150–300 bpm (depends on AV block) | 100–160 bpm | 100–160 bpm | | **AV relationship** | None | 2:1, 3:1, variable | 1:1 | 1:1 | ### Key Point: **Atrial fibrillation is characterized by the absence of organized P waves and an irregularly irregular ventricular rhythm.** The baseline shows fine or coarse fibrillatory waves (f waves) that represent chaotic atrial depolarization at rates of 400–600 bpm. The ventricular response is irregular because the AV node conducts impulses unpredictably. ### Clinical Pearl: **"Rapid ventricular response" in AF is defined as a ventricular rate >100 bpm at rest.** This patient's rate of 110–130 bpm is rapid and symptomatic (palpitations, dyspnea). Common precipitants in elderly patients include: - Acute infection (UTI, pneumonia) - Thyrotoxicosis - Acute coronary syndrome - Decompensated heart failure - Electrolyte disturbances ### High-Yield: - **Irregularly irregular rhythm is the hallmark** — no two consecutive R-R intervals are equal. This distinguishes AF from other arrhythmias. - **Stroke risk in AF:** Use CHA₂DS₂-VASc score. This patient (age 72, hypertension, diabetes) scores ≥2 and requires anticoagulation (unless contraindicated). - **Rate control vs. rhythm control:** Initial management focuses on rate control (beta-blockers, calcium channel blockers, digoxin) rather than immediate cardioversion, unless hemodynamically unstable. ### Mnemonic: **"Irregularly Irregular = AF"** — if the rhythm is chaotic and P waves are absent, think atrial fibrillation first.