Disturbances in Heart Rhythm

Disturbances in the heart rhythm, or arrhythmia, can cause irregular heartbeats.

If the heart rate falls below sixty beats per minute, it is called bradycardia, whereas a heart rate above one hundred is called tachycardia.

In ventricular tachycardia, the heart beats too fast, and the ventricles fail to pump sufficient blood, resulting in low blood pressure and heart failure.

An uncoordinated, asynchronous beating is termed fibrillation, which can be either atrial or ventricular.

In atrial fibrillation, the unsynchronized electrical activity causes the atria to quiver or fibrillate. The ECG appears as irregularly spaced QRS complexes and ill-defined P waves.

In contrast, ventricular fibrillation produces abnormal ECG deflections, leading to grossly abnormal waves and complexes. Chaotic electrical signals cause ventricles to quiver rather than contract. As a result, the ventricles stop pumping blood, resulting in circulatory failure.

Blocked electrical pathways between the atria and ventricles can cause heart block.

On an ECG, the first-degree AV block extends the P-Q intervals, while the second-degree block has fewer QRS complexes.

The third-degree or complete block reduces the ventricular beating to less than forty per minute.