Arrhythmias, Heart Blocks & Valvular Disease Explained

An arrhythmia is any abnormal heart rhythm — too fast, slow or irregular. A conduction block means the heart's electrical signal is delayed or stopped as it travels from the atria to the ventricles. Valvular heart disease means one of the four heart valves is narrowed (stenosis) so blood struggles through, or leaky (regurgitation) so blood flows backward.

These matter because some rhythms kill within minutes while others only need monitoring, and telling them apart on an ECG decides treatment. Complete block needs a pacemaker, AFib needs stroke prevention, tight valves need replacement. All three are diagnosed with tools available in any hospital — the ECG and the echocardiogram.

Key Concepts

• Atrial fibrillation (AFib): chaotic atrial activity with no P waves and an "irregularly irregular" pulse. Clots can form and cause stroke — prevented with anticoagulants guided by the CHA2DS2-VASc score.
• SVT and VT: SVT starts above the ventricles (regular, narrow); VT starts in the ventricles (wide-complex) and can degenerate into fatal fibrillation.
• AV blocks: first-degree (long PR, benign); Mobitz I (PR lengthens until a beat drops — usually benign); Mobitz II (sudden dropped beats — needs pacemaker); third-degree (atria and ventricles independent — urgent pacemaker).
• Mitral stenosis: usually rheumatic; the valve area shrinks from a normal 4–6 cm² toward under 1.0 cm² in severe disease. Produces an opening snap and diastolic rumble at the apex, with breathlessness as pressure backs into the lungs.
• Mitral regurgitation: a systolic murmur radiating to the armpit as blood leaks back into the left atrium.
• Aortic stenosis: syncope, angina and dyspnea with a harsh systolic ejection murmur; severe cases need valve replacement.
• Aortic regurgitation: an early diastolic murmur with a wide pulse pressure and bounding pulses.

Formulas

• Pulse deficit: pulse deficit = apical heart rate − radial pulse rate. In AFib some weak beats never reach the wrist, so a large deficit flags the arrhythmia at the bedside.
• Heart rate from ECG (300 method): heart rate = 300 ÷ number of large boxes between two R waves. Four large boxes means 300 ÷ 4 = 75 beats per minute.
• Mitral valve area thresholds: normal 4–6 cm²; severe stenosis is under 1.0 cm², measured on echocardiography.

Worked Example

1. A 65-year-old woman complains of palpitations. Her pulse feels completely irregular. The nurse counts the apical rate at 120/min and the radial pulse at 88/min.
2. Pulse deficit = 120 − 88 = 32 beats per minute — a large deficit, classic for atrial fibrillation, where weak contractions never reach the wrist.
3. The ECG confirms AFib: no P waves, irregularly irregular QRS complexes. Her CHA2DS2-VASc score indicates stroke risk, so she starts an anticoagulant plus a rate-controlling drug, and an echocardiogram checks her valves and heart function.

Common Misconceptions

• Myth: All palpitations are dangerous. Fact: many are benign extra beats; danger depends on the rhythm's type, rate and symptoms.
• Myth: A pacemaker strengthens a weak heart. Fact: it only fixes electrical timing; it does not improve the muscle's pumping power.
• Myth: Any murmur means a hole in the heart. Fact: most murmurs are valve flow sounds from stenosis or regurgitation, not septal defects.

Real-World Applications

• ECG technicians and emergency rooms: rapid rhythm and block recognition decides who needs a pacemaker tonight.
• Echocardiography labs: measure valve areas and leak severity to time surgery.
• Pacemaker clinics: lifelong follow-up of implanted devices.

Arrhythmias, conduction blocks and valve diseases are read on the ECG and echo: pulse deficit flags AFib, the 300 method gives the rate, and valve area under 1.0 cm² marks severe mitral stenosis. Mobitz II and complete block need pacemakers; AFib needs stroke prevention; tight valves eventually need replacement.