In this article, we will discuss the Diagnosis of Sick Sinus Syndrome. So, let’s get started.
The diagnosis of sick sinus syndrome is suspected on clinical grounds and correlated with ECG manifestation of sinus node dysfunction. SA node dysfunctions manifest SA blocks seen intermittently or constantly on the ECG as a pause created by cessation of atrial activity (the whole P-QRS-T complex is dropped. The tachycardia and bradycardia syndrome is also a manifestation of sick sinus syndrome characterized by alternating periods of tachyarrhythmias and bradyarrhythmias.
The most important step in diagnosis of sick sinus syndrome is to correlate symptoms with ECG manifestations of sinus node dysfunction. While ambulatory ECG (Holter’s) monitoring remains a mainstay in evaluation of sinus node dysfunction, most of the episodes of syncope are paroxysmal and unpredictable. Single and multiple 24-hour monitoring may fail to record a symptomatic period, therefore, provocative test (carotid sinus pressure, exercise test and pharmacological tests) are frequently helpful.
Carotid sinus pressure for 5 seconds producing a sinus pause >3 seconds on ECG indicates sinus node dysfunction. Similarly injection of atropine 1-2 mg I.V. will not accelerate the heart beyond 90/min in case of sinus node dysfunction but will do so in a vagotonemia (normal response). Similarly isoprenaline 1-2 mg I.V. may be employed to test structural nodal disease.
Electrophysiological studies (sinus node recovery time and sinoatrial conduction time) help in establishing the diagnosis the normal values are given below these parameters are recorded following pacing.
Sinus node recovery time (corrected for spontaneous heart rate) normally is less than 550 ms; prolongation indicates sinus node dysfunction in asymptomatic patients.
Sinoatrial conduction time: It is one half of the difference between the pores following termination of brief period of pacing and the sinus cycle length.