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An 81 year old patient was admitted for percutaneous mitral balloon valvotomy. His ECG showed sinus rhythm with first degree atrioventricular block (top panel). However, at transthoracic and transoesophageal echocardiography (upper middle panel) the mitral Doppler signal had no A wave of augmented flow during atrial systole. Transoesophageal imaging showed the left atrium (dimension 5.3 cm) inert, while the right atrium contracted vigorously. Similar findings were seen at left and right atrial angiography. At cardiac catheterisation transmitral pressure gradient showed no “a” wave of left atrial contraction. Following successful Inoue balloon dilatation an F6 pacing electrode, attached to the chest lead of the catheter table ECG system, was passed via a Mullins Sheath to the left atrium and recordings were made from several sites on the left atrial cavity wall: no electrical activity corresponding to the p wave of the surface ECG was seen (lower middle panel—50 mm/s). When repositioned against the right atrial wall large atrial depolarisations were recorded (bottom panel).
In this patient, who had no evidence of amyloid, left atrial standstill was obscured by the right and left atrial electrical dissociation. Long term warfarin treatment was mandatory because of the risk of left atrial thrombus.