Chapter 85: Ventricular Arrhythmias
You are seeing a 45-year-old man in consult for very frequent premature ventricular contractions (PVCs). You counsel the patient regarding his risk of developing a PVC-induced cardiomyopathy (CM). What is the lowest percentage of PVCs over a 24-hour period that is associated with a higher risk of developing CM?
The answer is C. (Hurst’s The Heart, 14th Edition, Chap. 84) Clinical evidence of an association between frequent PVCs and a dilated CM has been demonstrated.1-5 A higher burden of PVCs over a 24-hour period is associated with higher risk, but the development of CM associated with a burden as low as 10% has been described.1 Current studies regarding the role of PVCs in the development of a CM demonstrate the following: (1) left ventricular dysfunction can occur when PVCs are present for a prolonged period of time; (2) LV dysfunction occurs among patients with a high frequency of PVCs; and (3) among patients with a PVC-induced CM, LVEF improves in most patients when the PVCs can be eliminated with radiofrequency catheter ablation. A number of electrocardiographic and other factors have been associated with an increased risk of PVC-induced CM, but further assessment is ongoing. A higher burden, retrograde ventriculoatrial (VA) conduction,2 PVC QRS duration,3,7 site of origin,7 interpolation,5 male gender,4 PVCs throughout the day,4 epicardial origin,8 and coupling interval dispersion9 have been described as potential contributing factors.
A 48-year-old perimenopausal woman presents to the emergency department with incessant palpitations that have been occurring over the last month. Transthoracic echocardiogram is normal. An electrocardiogram reveals ventricular bigeminy and short runs of nonsustained ventricular tachycardia (VT). The morphology of the ventricular ectopy is as follows: LBBB morphology in V1 with a precordial transition at V5, an inferior axis, negative in aVL and aVR, and slight negativity in lead I. Regarding this type of VT, which of the following is false?
A. This arrhythmia is often provoked by exercise and emotional stress
B. In women, these occur more often during premenstrual, perimenopausal, and gestational periods
C. When RV dysfunction is present on transthoracic echo, a cardiac-MRI should be considered
D. The success rate for medical therapy is excellent
E. The proposed cellular mechanism is cyclic adenosine monophosphate–mediated (cAMP) triggered activity from delayed afterdepolarizations