A 35-year-old woman with known familial hypertrophic obstructive cardiomyopathy (HOCM) with severe, symptomatic resting and exertional left ventricular outflow tract (LVOT) gradient underwent assessment prior to elective myectomy. Hypertrophic obstructive cardiomyopathy was diagnosed aged 17 with primary prevention implantable cardioverter defibrillator (ICD) implanted 3 years earlier for syncope. Other relevant history included triple-negative breast carcinoma with surgery and adjuvant chemo-radiotherapy in remission and a treated left-arm, provoked deep venous thrombosis. Clinically, she had deteriorated with worsening exertional dyspnoea and pre-syncope and was unable to tolerate beta blocker therapy. Examination revealed a loud systolic murmur extenuated by the Valsalva manoeuvre. Electrocardiogram (ECG) showed non-pathological Q waves and diffuse T-wave inversion (Panel A ). Asymmetrical hypertrophy measuring 2.0 cm at the septum with systolic anterior motion (SAM) of the anterior mitral valve leaflet with obstruction in the LVOT was seen on 2D transthoracic echocardiogram (Panel B ) and M-mode (Panel C ). A resting peak gradient of 87 mmHg with mild mitral regurgitation (MR) increased with exercise to a peak gradient of 228 mmHg with worsening MR severity (Panel D ). Left ventricular (LV) apex, LVOT and aortic pressure tracings were recorded prior to surgery and demonstrated a peak-to-peak gradient from the LV apex to LVOT to be 85 mmHg (pre-angiography) and 79 mmHg (post angiography) (Panel E ) with LV obliteration during systole (Panel F ). Frequent ventricular ectopy during the procedure highlighted the Brokenbrough-Braunwald-Morrow sign: the paradoxical decrease in pulse pressure due to post-extrasystole potentiation whereby, according to the Frank-Starling curve, increased diastolic filling increases the LVOT obstruction by worsening the anterior mitral valve leaflet SAM. The patient went on to have an uncomplicated radical myectomy with abolition of SAM and residual LVOT gradient of 4 mmHg.
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Published online: February 16, 2017
Accepted: December 19, 2016
Received: November 9, 2016
© 2017 Published by Elsevier B.V. on behalf of Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ).