Extrasystoles can occur during both relaxation and contraction phases of the heart cycle.
* During Relaxation (Diastole): An extrasystole during diastole can be triggered by an ectopic beat originating in the atria or ventricles. This premature beat interrupts the normal relaxation and filling phase of the heart.
* During Contraction (Systole): An extrasystole can also occur during systole, particularly if the ectopic beat originates within the ventricle and is strong enough to override the normal contraction wave. This can result in a premature and forceful contraction of the ventricle.
Why the misconception might exist:
* Timing of Electrocardiogram (ECG) recordings: ECGs are often recorded during periods of relative rest, making it more likely to capture extrasystoles occurring during diastole.
* Clinical relevance: While extrasystoles can occur during either phase, they are often more clinically significant during diastole. This is because they can disrupt the normal filling of the ventricles, potentially leading to decreased cardiac output.
In summary: It's important to understand that extrasystoles can happen during both relaxation and contraction phases of the heart cycle. While the timing of their occurrence can influence their clinical significance, they are not limited to occurring only during relaxation.
