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A 45 year old woman presented with recurrent episodes of rapid non-sustained palpitations and associated dizziness. She had no significant medical history or family history of cardiac disease. Examination revealed a soft systolic murmur. ECG showed sinus rhythm with left ventricular hypertrophy on voltage criteria and inferolateral T wave changes. Transthoracic echocardiography demonstrated the unusual finding of mid-ventricular hypertrophic obstructive cardiomyopathy with systolic cavity obliteration at the papillary muscle level and an associated intracavity velocity of 4 m/s. There was sparing of the basal septum and the apex was not hypertrophied but rather thinned, asynergic, and aneursymal (fig 1). No thrombus was evident and no other wall motion abnormalities were present. Colour Doppler revealed a turbulent jet in both systole and early diastole with flow from apex to base. Continuous wave Doppler (fig 2) revealed systolic flow away from the transducer (apical four chamber position), then mid-ventricular cavity obstruction with no flow, followed by a high early diastolic velocity (4 m/s) and flow from apex to base concurrent with the mitral inflow E wave. This paradoxical early diastolic flow is thought to represent blood trapped in the apical cavity in systole, which subsequently leaves the apex in diastole when mid-ventricular obstruction is no longer present.
Several patterns of hypertrophic cardiomyopathy (HCM) have now been clearly defined. The apical variant constitutes 25% of all HCM in the Japanese population, but only 1–2% of the HCM cases in non-Japanese patients. Mid-ventricular HCM with apical asynergy is somewhat less common. In the largest published report to date, a Japanese team reported an incidence of concealed apical aneurysm with mid-ventricular cavity obliteration of approximately 1.5% of all HCM cases. The incidence in non-Japanese patients is yet to be clarified. The importance of this variant is its association with ventricular arrhythmias and systemic embolism, the latter occurring in 30% of patients. Identification of the paradoxical early diastolic flow from apex to base can be a marker of a sequestered apical chamber in patients with cavity obliteration, particularly when the apical cavity cannot readily be delineated by cross sectional echocardiography.
Following the echocardiographic findings in this patient, a 24 hour Holter monitor was performed and revealed self limiting runs of supraventricular tachycardia along with ventricular couplets, but no ventricular tachycardia. Her palpitations are now controlled on amiodarone.