Risks of Untreated Paroxysmal SVT
Untreated paroxysmal supraventricular tachycardia carries significant risks including tachycardia-mediated cardiomyopathy, syncope in 15% of patients, and in rare cases—particularly with pre-excitation syndromes—sudden cardiac death. 1
Life-Threatening Complications
Tachycardia-mediated cardiomyopathy is the most serious chronic complication, developing when SVT persists for weeks to months with a fast ventricular response. 1 This represents a reversible form of heart failure that can progress to permanent myocardial dysfunction if left untreated. 2
Syncope occurs in approximately 15% of patients, typically immediately after initiation of rapid SVT or during prolonged pauses following abrupt termination of the tachycardia. 1 This poses significant injury risk and impairs ability to perform activities of daily living, particularly driving. 1
Sudden cardiac death, while rare in typical SVT, becomes a critical concern in specific high-risk populations:
- Patients with Wolff-Parkinson-White syndrome who develop atrial fibrillation face risk of extremely rapid ventricular rates degenerating into ventricular fibrillation. 2
- In one study of asymptomatic pre-excitation patients, 2% developed ventricular fibrillation during follow-up, with an additional 9% experiencing malignant arrhythmias. 1
- Adults with congenital heart disease and SVT face significantly elevated sudden death risk. 2
Acute Hemodynamic Complications
Heart failure and pulmonary edema can develop acutely during prolonged episodes due to:
- Increased atrial pressures from atrial contraction against closed AV valves. 1
- Rapid heart rates causing acute pulmonary congestion. 2
- Release of atrial natriuretic peptide in response to elevated atrial pressures, manifesting as polyuria. 1
Myocardial ischemia results from the combination of increased myocardial oxygen demand and decreased coronary perfusion time during tachycardia. 2 This risk is particularly elevated in patients with concomitant structural heart disease such as valvular aortic stenosis or hypertrophic cardiomyopathy. 1
High-Risk Populations Requiring Urgent Evaluation
Patients with pre-excitation on ECG (Wolff-Parkinson-White pattern) and history of palpitations require immediate electrophysiological evaluation due to risk of significant morbidity and possibly sudden death. 1, 2 A clinical history of irregular paroxysmal palpitations in these patients strongly suggests episodes of atrial fibrillation, which can conduct rapidly over the accessory pathway. 1
Adults with congenital heart disease represent the highest-risk population, with SVT occurring in 10-20% of these patients and carrying significantly increased risk of heart failure, stroke, and sudden cardiac death. 2, 3 Particularly high-risk lesions include Ebstein anomaly, Tetralogy of Fallot, transposition of the great arteries, and atrial septal defects. 2
Symptom Burden and Quality of Life Impact
Beyond life-threatening complications, untreated SVT causes substantial morbidity through recurrent symptoms including palpitations (86% of patients), chest discomfort (47%), dyspnea (38%), lightheadedness, fatigue, and anxiety. 4 These symptoms vary with ventricular rate, underlying heart disease, episode duration, and individual patient perceptions. 1
Episodes of lightheadedness and syncope create obstacles to usual activities of daily living, particularly driving, significantly impairing quality of life. 1 Studies using the 36-Item Short-Form Health Survey demonstrate impairment in physical role functioning, general health perceptions, and emotional role functioning in untreated patients. 1
Critical Clinical Pitfall
The most dangerous pitfall is failing to recognize that SVT is not always benign. 4 While many patients tolerate episodes well, the presence of syncope, pre-excitation on ECG, congenital heart disease, or structural heart abnormalities mandates prompt referral to a cardiac arrhythmia specialist. 1 All patients with severe symptoms such as syncope or dyspnea during palpitations should be referred for prompt evaluation. 1