I wish to thank Arron Pearce, cardiac nurse and ECG analyst, for this month’s case. It concerns a 30-year-old male who presented with dizziness, chest tightness and palpitations. Figure 1 shows the presenting ECG and figure 2 a follow-up ECG recorded a few weeks later.

Please note: all of the limb leads in the 12-lead display show the same 2.5 seconds of ECG. The rhythm strip shows a sequential 10-second recording of lead II.

What is your diagnosis? Please provide your reasons.

Figure 1: Initial ECG recorded during chest tightness, dizziness and palpitations

Figure 2: Follow-up ECG recorded a few weeks later

ANSWER

NOTE: Answer added 21.03.24

We’ll start with the first ECG. This shows a regular, broad-QRS tachycardia at a rate of 250 bpm and the assumption must be that this is VT. But there is more we can say about the ECG. The QRS has a LBBB morphology, which means that the tachycardia originates from the right ventricle. One tachycardia that has a LBBB morphology is right ventricular outflow tract (RVOT) VT. This is the most common of the so-called idiopathic VTs – relatively benign tachycardias that occur in people with structurally normal hearts – but RVOT VT is characterised not only by a LBBB morphology but by an inferior QRS axis too, and that’s not what we see here. Here the QRS axis is about -30 degrees, so the ventricular forces are directed somewhat to the left rather than inferiorly. The tachycardia therefore originates in the RV, but not the RVOT.

Let’s now move on to the second ECG. This shows sinus bradycardia at 53 bpm with normal QRS axis, T wave inversion in III and aVF, a biphasic T wave in II, and T wave inversion from V1 to V5. There is also an rSr’ complex in V1, with a duration of 120 ms; a very small positive deflection after the R wave in V2; and a slightly slurred upstroke to the S wave in V3 and V4. What is the cause of the wide rSr’ complex in V1? It would be easy to attribute this to RBBB, but the T wave inversion here is far more extensive than we would expect to see in RBBB. In RBBB there is normally T wave inversion in those chest leads where the 2nd R wave is dominant – usually only V1. So, if this is not RBBB, what is it? This is a case of arrhythmogenic right ventricular cardiomyopathy (ARVC), a progressive, genetic condition in which healthy RV myocardium is replaced by fat or fibrofatty tissue, with myocardial inflammation and scarring and loss of contractile function. This can result in segmental aneurysmal dilation of the RV, with the areas of RV disease providing foci for potentially lethal ventricular arrhythmias. In many, if not most, cases there is involvement of the left ventricular myocardium as well, and evidence of this is provided by widespread T wave inversion.

The patchy RV disease causes delayed depolarisation of areas of RV myocardium, resulting in late deflections on the end of the QRS in chest leads that overlie the RV. A small positive deflection on the end of the QRS, as seen in V2 in figure 3, in ARVC is known as an epsilon wave but the delayed RV depolarisation can also cause a slurring or ‘jerkiness’ of the upstroke of the S wave, as seen in V3 here. The second R wave in V1 could be regarded as a big epsilon wave since it also is due to delayed RV activation, and the reason the QRS in V1 is similar to that seen in RBBB can easily be understood if we recall the reason for the typical QRS morphology in V1 in RBBB. In RBBB, because of a conduction abnormality, depolarisation of the RV is delayed and prolonged, resulting in a tall, broad second R wave. In ARVC, because of disease of the RV myocardium, depolarisation of regions of the RV is also delayed and prolonged and this may lead to an epsilon wave or a second R wave in V1.

Figure 3. Close-up of V1-V3, showing evidence of delayed RV depolarisation.

The diagnosis of ARVC was confirmed in this patient and he received an implantable defibrillator to prevent arrhythmic sudden death.

Thanks again to Arron Pearce for supplying the ECGs and clinical history, and to everyone who participated in the discussion.

Dave Richley