Tachycardia

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Introduction

Tachycardia's are arranged as follows;

Differentiation between SVT and VT

To differentiate between supraventricular tachycardias and ventricular tachycardias a 12 lead ECG is the cornerstone of the diagnostic process. At first, the physician has to make a differentiation between a small or broad complex tachycardia.

Definitions:

Small complex tachycardia:

QRS duration < 120 ms.

A small complex tachycardia is most likely to be a SVT. However, also a septal VT or His-tachycardia can appear as a small complex tachycardia.

Broad complex tachycardia:

QRS duration > 120 ms.

A broad complex tachycardia can be due to a SVT with aberration, pre-exited tachycardia (eg antidrome re-entry tachycardia) or VT.

Differentiation:

(Figure 1, small complex tachy algorithm) (Figure 2, broad complex tachy algorithm)

Treatment:

Haemodynamical instability (high heartrate, low blood pressure):

• electrical cardioversion

Haemodynamical stability in a regular small complex tachycardia:

• Carotid massage (after palpation and ausculatation of carotid arteries for exclusion of carotid occlusion/stenosis)
• Vasalva manoevre
• Adenosine bolus (if patient is not asthmatic or having COPD)
• Verapamil (if patient is not having systolic heart failure)
• Beta-blocker (if patient is not having systolic heart failure)

Haemodynamical stability in a regular monomorphic broadcomplex tachycardia (systolic blood pressure >100 mmHg:

• Procaïnamide
• Amiodaron