Ventricular Tachycardia and Acute Myocardial Infarction

The first tracing shows a wide complex tachycardia at a rate of about 280/min. The morphology is like a left bundle branch conduction block with concordance of the precordial leads with mostly negative deflections. Negative P waves can be seen in lead AVR. The patient is 35 years old, has chest pain, there was no response to adenonsine and the arrhythmia terminates with lidocaine.

The differential diagnosis here is ventricular tachycardia, ventricular pre-excitation with flutter and 1:1 conduction or a fast SVT with A/V conduction down the accessory pathway, atrial flutter with 1:1 conduction and bundle branch block, or a fast SVT with a bundle branch block.

Looking at the morphology of the QRS we note a wide R in V2 suggestive of VT but do not see notching of the downstroke of V2 which is another sign of VT with a LBBB morphology. The most important observation is the independent P wave activity in lead AVR which rules out SVT or atrial flutter with aberrancy or pre-excitation. The electrocardiogram suggests ventricular tachycardia. Further the failure of adenosine to terminate or slow the tachycardia to reveal the atrial activity suggests ventricular tachycardia (note some VTs such as right ventricular outflow tract VTs can terminate with adenosine!). Finally the response to lidocaine suggests ventricular tachycardia.

The second tracing shows sinus tachycardia at about 120/min with ST elevation in the inferior leads and ST depression in the anterior leads. There are also inferior Q waves, with a Q wave in AVF wider than 30ms. The EKG suggests an acute inferior myocardial infarction (see more examples of EKG and myocardial infarction). This was confirmed with serial blood tests in the hospital. It is interesting to note that the Q wave in AVF is probably new and appeared early in the course of this infarction. Dr. M. Rosengarten

Comments from the Web:

T.A.@Hotmail.com: The ECG shown is probably ventricular tachycardia in the context of inferior wall MI, that broke with the use of lidocaine.

P.M. @zaz.com.br:

It is tempting to call this SVT because of the young age of the patient. One can see chest discomfort with SVT in patients with tachycardias. One must remember thought that SVT is becoming more and more rare because of ablation (see WPW ablation for SVT and AVNRT ablation for SVT) and hence it is best in most cases to think of VT first. Dr. M. Rosengarten

A.P. @saol.com: The wide complex tachy hints at being of ventricular origin if one notices the notching of the QRS .The failure to respond to adenosine is not surprising .The 2nd ECG clearly shows an inferior infarct with reciprocal changes. The diagnosis is ventricular tachycardia . The pulseless patient must be treated as VF . The patient with a pulse must be treated with lignocaine 1 - 1.5 mg/kg .

S.L.@selcon.com.au: My assessment of the ECG at first glance would make me think of Ventricular Tachycardia caused by a massive inferior MI which is why it responded to Lignocaine and not Adenosine.

D.D. @dynamite.com.au: THE FIRST ECG SHOWS VT, WITH A RAPID VENTRICULAR RATE. GIVEN THE HISTORY OF SEVERAL HOURS CHEST PAIN, ONE WOULD ASSUME THAT THE PATIENT HAS BEEN IN THIS RHYTHM FOR THIS TIME. THUS, ONE MIGHT EXCLUDE IT, AS BEING A PARADOXICAL SVT. THAT IS PROBABLY WHY THIS ARRHYTHMIA RESPONDED WELL TO LIGNOCAINE RATHER THAN ADENOSINE.

The chest pain probably came before the VT and was related to the acute inferior wall myocardial infarction. Although possible it is probably rare to induce a myocardial infarction as a result of a tachycardia. The key might be to ask the patient which came first. Adenosine and lidocaine are probably the safest medications to use with a fast wide complex tachycardia. Verapamil should be avoided as it can cause a cardiac arrest in patients with VT. Dr. M. Rosengarten

D.S.@moffitt.usf.edu:

The rate in the first tracing is really too high for a sinus tachycardia athough in some case sinus tachycardia can reach rate of 170/min and more (e.g. exercise induced tachycardia)Dr. M. Rosengarten

S.U.@md3.vsnl.net.in: ECG SHOWS acute inf.myocardial infarction with possible posterolateral extension.initially presented with ventricular tachycardia,now there is residual LAHB.

Left anterior hemi-block is a left axis deviation of the QRS to more than -30 degrees. This makes the S wave in lead dII larger than the R wave. This is not the case here.Dr. M. Rosengarten