The perception of heartbeat sensations is a common, everyday physical experience that can range from completely normal physiological awareness to symptoms of abnormal heart rhythms, requiring no citation as it is a matter of basic medical observation.
The claim addresses basic physiological awareness and medical presentations of palpitations, which are a matter of everyday clinical observation and common medical knowledge. The retrieved papers discuss tangential topics such as cardiac tumors, interoceptive accuracy, and ventricular tachycardia, but a direct literature receipt is unnecessary for such a foundational and universally recognized medical truism.