Ventricular tachycardia diagnosis

Theuns DAMJ, Rivero-Ayerza M, Goedhart DM, van der Perk R, and Jordaens LJ. Evalution of morphology discrimination for ventricular tachycardia diagnosis in implantable cardioverter-defibriUators. Heart Rhythm 2006 3 1332-1338. 

Make a firm diagnosis. A firm arrhythmia diagnosis should be established. For example, the misuse of verapamil in patients with ventricular tachycardia mistakenly diagnosed as supraventricular tachycardia can lead to catastrophic hypotension and cardiac arrest. As increasingly sophisticated methods to characterize underlying arrhythmia mechanisms become available and are validated, it may be possible to direct certain drugs toward specific arrhythmia mechanisms. 

ADENOSINE Adenosine (adenocard) is a nucleoside that is administered as a rapid intravenous bolus for the acute termination of reentrant supraventricular arrhythmias. Rare cases of ventricular tachycardia in patients with otherwise normal hearts are thought to be DAD-mediated and can be terminated by adenosine. Adenosine also has been used to produce controlled hypotension during some surgical procedures and in the diagnosis of coronary artery disease. 

Bretylium tosylate is frequently used in the treatment of ventricular arrhythmias which are refractory to other anti-arrhythmic drugs. It is specifically useful in the diagnosis of ventricular tachycardia. 

C. Differential diagnosis. Rule out the following possible causes of ventricular premature beats, ventricular tachycardia, or ventricular fibrillation ... 

IV. Diagnosis is based on a history of exposure and typical cardiotoxic features such as QRS and QT interval prolongation, AV block, or polymorphous ventricular tachycardia. 

Wrong diagnosis of ventricular tachycardia on ECG with electrical artefact simulating dysrhythymia Inadequate knowledge... 

Adenosine is the treatment of choice for diagnosis and reversal of supraventricular arrhythmias. Verapamil is an alternative for the management of narrow complex tachycardias. Amiodarone is the most effective drug at reversing atrial fibrillation, and in prevention of ventricular arrhythmias, but has several adverse effects. 

Fig. 19.14 Stored atrial and ventricular electrogram from a patient with a Guidant Discovery pacemaker. Although the system interpreted the atrial rate as a paroxysmal supraventricular tachycardia, the close correlation between the atrial and ventricular rates, the PR interval as measured from the recording, and the normal rate identifies this as a normal rhythm. Hence, atrial sensing of the far field R wave probably accounted for the system s diagnosis. Knowing this, one can more effectively program the pacemaker and know how to interpret some of its reports.

A sudden onset function will not likely be of much use for the ICD to discriminate AT from VT since both can initiate in this fashion. A ventricular morphology or width discriminator may help, again in the absence of BBA. Not all ATs conduct each beat to the ventricles, so this information ( P waves > R waves) in a dual chamber ICD event recording may allow the interpreter to help rule in the diagnosis of SVT. It should be noted that dual tachycardias, i.e. SVT and VT, can coexist in which the number of registered P waves is still greater then the number of registered R waves. 

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