Premature ventricular contractions (PVCs) are some of the many causes of palpitations. On one or several occasions, you may feel your heart pulsating, usually during periods of exercise, anger, or anxiety. However, your heartbeat will be regular despite its increased frequency and intensity. But, during similar situations, you may feel one or two extra heartbeats that do not follow the synchrony – escape beats, or you notice that the heart pauses before the heartbeat becomes regular again. You, perhaps, perceive these as palpitations or irregular heartbeats – that should probably bother you, but to what extent.
For premature ventricular contractions to occur, Purkinje fibres, instead of the sinoatrial node, initiate a heartbeat. Are you confused? Let’s break it down.
The heart relies on a pattern of electrical activity, which travels through the myocardium to contract and pump blood around your body.
The human heart has four chambers: two atria and two ventricles. The vena cava returns blood from the rest of the body to the right atrium, which pushes it down to the right ventricle. Upon contraction, this blood leaves the heart to pick oxygen from the lungs: it then returns to the heart via the pulmonary vein to enter the left atrium, then left ventricle, which eventually pumps it to the rest of the body via the aorta. These series of events constitute what we call a cardiac cycle. They happen for every heartbeat.
The electrical signal that drives the cardiac cycle starts in a specialised group of cells in the right atrium (pacemaker cells), at the sinoatrial node. Through pertinent pathways, the electrical signal reaches another group of cells located at the junction between the atria and ventricles, the atrioventricular node. From here, it is propagated along with a series of conduction pathways – the bundle of His and Purkinje fibres – to reach the ventricles to enable them to contract and pump out blood simultaneously to the lungs and rest of the body.
Any electrical signal from any area within the heart other than the sinoatrial node leads to an extra heartbeat. For example, the Purkinje fibres may initiate a heartbeat. Because of the anomaly, the ventricles contract before or after a signal from the sinoatrial node. Two heartbeats cannot occur in tandem. So, you perceive this as a pause that happens before or after a series of regular heartbeats. This ordeal constitutes a premature ventricular contraction.
You may get premature ventricular contractions, one at a time, or in a repetitive fashion: doublets for two; triplets for three; three or more constitute ventricular tachycardia. If you have a PVC that follows every heartbeat, we call it bigeminy. If it occurs after every third heartbeat, it is trigeminy.
Amidst all these fracases, what you perceive are palpitations. You may feel nothing at all (asymptomatic). You may be lightheaded, have shortness of breath, chest pain, and anxiety. On rare occasions, you get syncope.
Clinicians may find an irregular pulse, hypotension, or nothing significant. They will inquire about any drugs you’ve used before and examine you for any problems in your heart or any other body organ.
For the large part, there’s no identifiable cause to such palpitations: they resolve spontaneously. But this isn’t your call to make: it’s the clinician’s, preferably, a cardiologist.
Nevertheless, there are a few causes that are worth mentioning. Anxiety, electrolyte imbalances, and excess caffeine intake: alcohol, illicit drug use, high levels of catecholamines (adrenaline, noradrenaline), and sleep deprivation. Electrolyte imbalances of concern are low potassium, magnesium, and high blood calcium.
Diseases associated with PVCs include cardiomyopathy, myocardial infarction, mitral valve prolapse, hypertension, hyperthyroidism, and anaemia. Also, conditions that alter the status quo of the fibres that propagate electrical signals within the heart have the propensity to cause PVCs.
Healthy people experience premature ventricular contractions on one or several occasions. They occur at a rate of 1 – 4% when using electrocardiography (ECG) or 40 – 75% on a 24 – 48-hour ECG monitor (Holter).
An ECG is the gold-standard tool to ascertain the presence of extra heartbeats. But, since they may be infrequent, we may not observe any. It is when a Holter monitor comes in handy to evaluate your heart’s electrical activity for about 24 to 48 hours. A cardiologist performs and interprets it. We will request a complete blood count to rule out anaemia: thyroid function tests and electrolytes to assess thyroid function and electrolyte imbalances. On a few occasions, we may do an echocardiogram to ascertain the structural integrity of your heart.
When PVCs cause no symptoms, we do not suggest any treatment. We treat any precipitant we have identified and tackle risk factors like excess caffeine intake and anxiety. We commonly employ drugs that prevent abnormal heart rhythms and stabilise the heart – antiarrhythmics, beta-blockers, and calcium channel blockers. If your PVCs recur or are refractory to conventional therapy, an electrophysiologist may ablate the area of the fibres generating them.
Without an underlying heart disease, premature ventricular contractions won’t kill you: only those who experience abnormally episodes (> 1000/day) are at risk of cardiomyopathy. To note, if you experience PVCs during an exercise, you shouldn’t worry. The contrary is true if they occur after exercise. You may be at an increased risk of death from underlying undiagnosed heart disease.
Never stay put upon experiencing premature ventricular contractions. Visit a clinician to delineate the cause. Curb down on the caffeine and alcohol you are taking. Eat a healthy diet and avoid excessive periods of anxiety. PVCs are manageable.
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