Ventricular Tachycardia - Dr Magdi M Saba

Dr Magdi M. Saba, Consultant in Cardiac Electrophysiology and Senior Lecturer at St George's University of London, UK, talks to Cardio Debate about Ventricular Tachycardia.

Transcript

What are the criteria that define high risk VT?

The criteria that define high risk ventricular tachyarrhythmias are multiple, but if we come to think about ventricular tachycardia and its main cause it’s probably ischaemic heart disease and scar. So scar-related ventricular tachycardia is probably the most serious thing we’re looking for.

So I would suggest when we see a patient with ventricular tachycardia the first thing we want to know is what their ejection fraction looks like, if they have a history of coronary disease, myocardial infarction – so an echocardiogram, would show us some areas of hypokinesia, akinesia, or even an ECG that shows you where the Q-waves are. Prior history of ischaemic heart disease is very telling – and that’s a typical high-risk patient with ventricular tachycardia.

And other causes of ventricular tachycardia such as cardiomyopathies, non-ischaemic cardiomyopathies such as, for example arrhythmogenic cardiomyopathy, which affects mainly the right ventricle but could also involve the left ventricle, are high risk features.

The way to diagnose is a little bit more tricky. There’s ECG criteria, major and minor criteria on cardiac imaging, so cardiac MRI in that instance would probably be helpful.

And depending on the type of ventricular tachycardia we see, we can look at the ECG and say whether it is left ventricular or right ventricular. And the age of the patient, and their history – we can typically define the patient who needs further imaging.

There are less risky forms of VT – a VT that involves normal hearts, or ostensibly normal hearts on echo, typically from the outflow tracts. The right ventricular outflow tract, occasionally from the papillary muscles, and these are labeled as ‘normal heart VTs’. Of course there is something abnormal about them, but normal in terms of structure and no evidence of scar or infiltrative disease.

Is the R/T phenomenon a marker of risk?

So the R/T phenomenon is something that we see very occasionally. It’s a premature ventricular complex that happens on the T-wave, somewhere in the vulnerable window around the peak of the T-wave – just before or after the peak.

And it can lead to a fast ventricular arrhythmia, typically ventricular fibrillation. Not monomorphic VT, it’s usually related to triggered activity, not automaticity, and it can frequently occur with drug-related issues.

We don’t see it clinically that often. It’s not something that we tend to worry about in terms of the coupling interval of the ectopic beat, they typically occur after the T-wave. But when we see it happen, or if we see brief runs of non-sustained VT after that phenomenon we tend to worry about them a little bit more – but fortunately it’s not that common.

And the way to risk stratify these patients would be with a treadmill test, for example, also an ECG to see if there is anything we can predict. If on an exercise treadmill test, for example, there is more ectopy, triggered activity and more disorganised ventricular arrhythmia then these would be high risk features. But again this is not something we see that often.

Current therapeutic approaches for high risk VT

The methods we have at our disposal to treat ventricular arrhythmias are multiple. Fortunately we are in a technologically-advanced state compared to 20 years ago.

So let’s take a patient with VT. A middle-aged person with a prior history or myocardial infarction, the typical scenario.

We get an echocardiogram, we confirm, let’s say, there’s an anterior wall scar. We confirm this with an MRI to really define the topography of the scar, how deep it is, “transmural”, the patient will ultimately get a defibrillator because that’s indicated for secondary prevention. So that’s probably the mainstay, is to have the back-up of a defibrillator, an ICD implantable cardioverter defibrillator to protect them from sudden death. That’s number one.

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