A popular belief among clinicians is that supraventricular tachycardia (SVT) is usually benign. However, the incidence of disabling symptoms in patients with SVT has not been widely investigated. These researchers found that, despite a low incidence of associated heart disease and good left ventricular function, there was a high frequency of disabling, potentially life-threatening symptoms associated with SVT in a sample of 167 patients with SVT admitted for radiofrequency ablation.

This study was designed to:

• describe clinical symptoms in patients with SVT
• document the incidence of sudden death, syncope and other disabling symptoms
• determine whether these symptoms differ by tachycardia mechanism
• identify predictor variables of syncope

Data were collected from chart reviews of 167 consecutive patients with SVT admitted for radiofrequency ablation. Overall, the most frequent symptoms were palpitations (96%), dizziness (75%), and shortness of breath (47%).

The investigators found that 33 subjects (20%) reported at least one episode of syncope which was preceded by palpitations. Severe presyncope requiring abrupt cessation of activities was reported by 35% of patients. Twenty six patients (16%) required at least one external direct-current shock for arrhythmia management. Three patients (2%) had nonlethal cardiac arrest and Wolff-Parkinson-White syndrome. The authors also noted that other studies have reported frequencies for aborted sudden cardiac death of 2% to 4.5% in SVT patient samples.

Tachycardia mechanism was tabulated as follows: atrioventricular nodal reentrant tachycardia (AVNRT) in 64 patients, atrioventricular-reciprocating tachycardia (AVRT) in 59 patients, atrial tachycardia in 22 patients and atrial flutter in 22 patients. Statistically significant differences in gender and age were noted between the groups, as follows.

*WPW=Wolff-Parkinson-White Syndrome
^†p=0.001

The symptom profiles of patients with AVNRT, AVRT and atrial tachycardia were very similar. Among patients with atrial flutter, the frequency of palpitations was significantly lower than the other groups (p=0.005) and a higher proportion of subjects experienced shortness of breath and fatigue. There were no significant differences in the incidence or frequency of syncope among the groups. The frequency of coronary artery disease, hypertension, valvular disease and congestive heart failure was statistically higher (p=0.003) in the atrial flutter group.

Heart rate of > or = 170 bpm was the only independent risk factor for syncope. The researchers reported that heart rate during syncope appeared to be a more important factor than mechanism of SVT. Of the 33 patients with a history of syncope, 71% were women and 29% were men. Syncopal episodes were always preceded by palpitations and occasionally some degree of dyspnea and chest discomfort.

[Editor's note: Since this study involved a cohort of patients referred for radiofrequency treatment of SVT, it is likely that their symptoms were more severe than those experienced by many other patients with SVT.]

The investigators concluded that "SVT can have potentially lethal consequences, and is more disruptive than previously thought."