<prompt> a wave is absent inAtrial fibrillationHeart blockTricuspid regurgitationPericardial effusion  <response>: A a wave of JVP: Due to right atrial contraction Synchronous with carotid artery pulse Absent a wave: Atrial fibrillation Diminished a wave: Tachycardia; Prolonged PR interval a Wave Fused with c Wave: Supra ventricular tachycardia Large a Waves: Pulmonary hypertension Pulmonary stenosis; Tricuspid stenosis Tricuspid atresia; AV dissociation Cannon Waves Giant a Waves: Complete heart block when right atrium occasionally contracts against closed tricuspid valve Ventricular tachycardia; Ectopic beats 