Ventricular arrhythmias are extra heart beats that originate from the lower cardiac chambers (ventricles). They can be asymptomatic or can cause palpitations (an awareness of heartbeat), chest pain, shortness of breath, lightheadedness, dizziness, or syncope (passing out).
These can occur in several different varieties: premature ventricular contractions (PVCs, also known as “skipped beats”), non-sustained ventricular tachycardia (NSVT), and sustained ventricular tachycardia (VT). A PVC is an isolated extra heartbeat, is rarely symptomatic, and is completely benign. Ventricular tachycardia refers to a number of extra beats that occur consecutively and are very fast. (Tachycardia means a rapid heartbeat). Sustained ventricular arrhythmias (lasting more than 30 seconds) can be life-threatening and cause sudden cardiac arrest. Certain medications, such as carvedilol (which he is taking), can suppress these abnormal rhythms.
In general, an implanted cardioverter defibrillator (ICD) can detect any serious ventricular arrhythmia (such as a sustained ventricular tachycardia) and convert it back to a normal rhythm using a small internal electrical shock. An ICD is implanted in a similar manner as a pacemaker, using a minor outpatient surgical procedure under the skin of the chest. Implanted defibrillators have been proven to reduce cardiac mortality and prolong life in patients who suffer from chronic congestive heart failure. They are recommended for those who have weakened heart function, with a reduced ejection fraction (EF) of less than 35% (again, normal is 50-60%).
A biventricular pacemaker is a feature often included in modern implanted defibrillators. A biventricular pacemaker utilizes an additional pacemaker wire that electrically stimulates (paces) a second part of the heart. It therefore paces both ventricles (the right and the left), rather than just one ventricle, which is the usual pacemaker configuration. This allows both sides of the heart to beat simultaneously. Most contemporary devices combine both a biventricular pacemaker with a defibrillator (ICD) in the same unit.
In patients who have a cardiomyopathy and CHF symptoms, the biventricular pacemaker feature has been proven to improve CHF symptoms, and even prolong life. It has also been shown to increase the strength of the heart pumping function, and commonly will improve the EF in CHF patients.
Pacemaker or defibrillator medical expert witness specialties include cardiology and cardiac electrophysiology.