14.6 : ECG Interpretation of Arrhythmias I: Sinus Arrhythmias

Arrhythmias are disturbances in the heart's rhythm that lead to abnormal heartbeats. These irregularities can originate from different parts of the heart and are classified based on their origin and nature.

Types of Arrhythmias

Sinus Node Arrhythmias

Sinus Bradycardia: Originating from the sinoatrial (SA) node, sinus bradycardia involves slower impulses, resulting in a heart rate of less than 60 beats per minute (bpm). Causes include sleep, vagal stimulation, beta-blockers, hypothyroidism, and myocardial infarction. On an ECG, sinus bradycardia presents with regular P waves, a consistent P-QRS-T pattern, and a less than 60 bpm rate. Treatment involves addressing the underlying causes, discontinuing causative medications, and using atropine if needed. Severe cases may require a pacemaker.

Sinus Tachycardia: Also originating from the SA node, sinus tachycardia involves faster impulses, leading to a heart rate greater than 100 bpm. It can be triggered by stress, fever, anemia, heart failure, stimulants, dehydration, and hyperthyroidism. The ECG shows regular P waves, a consistent P-QRS-T pattern, and a rate exceeding 100 bpm. Treatment is based on addressing the underlying causes and, if necessary, administering beta-blockers or calcium channel blockers.

Clinical Significance

Arrhythmias disrupt the heart's ability to pump blood effectively, causing symptoms such as palpitations, dizziness, shortness of breath, syncope, or sudden cardiac arrest. Treatment depends on the type and severity of the arrhythmia, emphasizing the importance of proper diagnosis and management to minimize risks and improve outcomes.