Lesson topic №25. Нарушения ритма (Cardiac arrhythmia in the outpatient setting)

Supraventricular tachycardia: classification

The term ‘narrow QRS tachycardia’ indicates those with a QRS duration ≤120 ms. A wide QRS tachycardia refers to one with a QRS duration >120 ms

In clinical practice, SVT may present as narrow or wide QRS tachycardias, most of which, although not invariably, manifest as regular rhythms.

Supraventricular tachycardia: differential diagnosis

Narrow QRS (≤120 ms) tachycardias

Regular

•Physiological sinus tachycardia

•Inappropriate sinus tachycardia

•Sinus nodal re-entrant tachycardia

•Focal AT

•Atrial flutter with fixed AV conduction

•AVNRT

•JET (or other non-re-entrant variants)

•Orthodromic AVRT

•Idiopathic VT (especially high septal VT)

Irregular

•AF

•Focal AT or atrial flutter with varying AV block

•Multifocal AT

Supraventricular tachycardia: differential diagnosis

Wide QRS (>120 ms) tachycardias

Regular

•VT/flutter

•Ventricular paced rhythm

•Antidromic AVRT

•SVTs with aberration/BBB (pre-existing or rate-dependent during tachycardia)

•Atrial or junctional tachycardia with pre-excitation/bystander AP

•SVT with QRS widening due to electrolyte disturbance or antiarrhythmic drugs

Irregular

•AF or atrial flutter or focal AT with varying block conducted with aberration

•Antidromic AV re-entrant tachycardia due to a nodo-ventricular/fascicular AP with variable VA conduction

•Pre-excited AF

•Polymorphic VT

•Torsade de pointes

•Ventricular fibrillation

Supraventricular tachycardia: clinical presentation

SVT may result in palpitations, fatigue, lightheadedness, chest discomfort, dyspnoea, and altered consciousness.

Direct risks due to SVT are unusual, but in specific situations (e.g. in patients with WPW syndrome and AF, or after atrial switch operation) may lead to sudden cardiac death.

SVT may be unrecognized at initial medical evaluation and the clinical characteristics can mimic panic disorder.

Supraventricular tachycardia: evaluation

Complete history taking, including family history, and physical examination are essential.

Full blood counts and a biochemistry profile—including renal function, electrolytes, and thyroid function tests—can be useful in specific cases.

An ECG recorded during tachycardia is ideal, and patients should be encouraged to seek medical assistance during episodes.

It may be useful to do 24 h ECG recordings, but tachycardia episodes are usually sporadic and may not be frequent enough to be recorded on ambulatory monitoring.

Transthoracic echocardiography

Supraventricular tachycardia: differential diagnosis of narrow QRS tachycardia

Supraventricular tachycardia: differential diagnosis of wide QRS tachycardia

The correct diagnosis of a VT is critical to management, as misdiagnosis and administration of drugs usually utilized for SVT can be harmful for patients in VT.

Therefore, the default diagnosis should be VT until proven otherwise!

Supraventricular tachycardia: differential diagnosis of wide QRS tachycardia

Key electrocardiographic criteria that suggest ventricular tachycardia rather than supraventricular tachycardia in wide complex tachycardia

Supraventricular tachycardia: differential diagnosis of wide QRS tachycardia

Key electrocardiographic criteria that suggest ventricular tachycardia rather than supraventricular tachycardia in wide complex tachycardia

Supraventricular tachycardia: differential diagnosis of wide QRS tachycardia