Description

Mitral annular calcification (MAC) is rapidly growing as a valvular heart disease with significant epidemiological impact1 as the population ages and the survival of patients with established risk factors (diabetes, hypertension, renal dysfunction) improves.2 Here, we discuss an unusual clinical presentation in a patient with MAC.

Our patient is a woman in her 50s with chronic kidney disease (baseline serum creatinine of 3.1 mg/dL and an estimated glomerular filtration rate of 28 mL/min/1.73 m²) and hypertension on medical follow-up. She was referred for cardiac examination with the progressive dyspnoea on exertion for the prior 8 months, with symptoms on less than ordinary physical activity (New York Heart Association class 3). She now presented to our clinic with an episode of syncope while on her evening walk. Physical examination was significant for a slow-rising pulse, a heaving apex impulse and a late-peaking, grade 3 ejection systolic murmur best heard at the left second intercostal space with no radiation to the carotids.

Baseline blood investigations demonstrated a normocytic, normochromic anaemia (haemoglobin 97 g/L), subtherapeutic vitamin D₂ (7 ng/mL) and elevated parathyroid hormone levels (108 pg/mL), with normal calcium and phosphate levels. Transthoracic echocardiography demonstrated dense MAC with haemodynamically significant mitral stenosis (with an estimated mitral valve area by the continuity method of 1.0 cm²) and mild mitral regurgitation with estimated pulmonary artery systolic pressures of 55 mm Hg (consistent with moderate pulmonary hypertension). The presence of concentric left ventricular hypertrophy with a preserved systolic function prompted a close search for a pathology increasing the left ventricular afterload. A subvalvular fixed left ventricular outflow tract (LVOT) peak gradient of 73 mm Hg (figure 1) was noted secondary to extension of calcium into the LVOT. Transoesophageal echocardiography confirmed the findings on transthoracic imaging and better delineated the anatomy of the outflow tract region (video 1). Gated cardiac CT demonstrated horseshoe annular calcium with involvement of both mitral leaflets and both fibrous trigones (figure 2).

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Figure 1

Two dimensional transthoracic echocardiography with continuous wave Doppler across the aortic valve demonstrating a parabolic dense curve with a peak gradient of 73 mm Hg consistent with a severe fixed left ventricular outflow tract obstruction.

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Figure 2

Gated non-contrast cardiac CT demonstrating horseshoe annular calcium with involvement of both mitral leaflets and both fibrous trigones.

While a variety of pathological consequences of MAC including mitral stenosis, mitral regurgitation, atrial fibrillation, stroke, pulmonary arterial hypertension and infective endocarditis are well recognised3 4 compromise of adjacent structures including the LVOT, coronary arteries and the conduction system is less well established.

Here, we report a case of resting LVOT obstruction caused by extensive MAC. The presence of concentric left ventricular hypertrophy and a sigmoidal septal morphology may have worsened the obstruction. Intervention for significant LVOT obstruction is generally considered for a resting or provoked gradient of ≥50 mm Hg. Our patient was thus planned for surgical intervention with debridement and prosthetic mitral valve implantation.

The presence of fixed resting, symptomatic LVOT obstruction secondary to extensive MAC is a rare entity previously noted anecdotally.5 6 This case demonstrates the importance of multimodality imaging in establishing the mechanism of LVOT obstruction as well as in planning intervention in such patients.