Case of trileaflet mitral valve: an important differential for non-classical intracavitary gradient in suspected hypertrophic cardiomyopathy

Abstract

There are nine published reports of trileaflet mitral valves globally. As such their implication on health outcomes and associations with other disease is uncertain. This case describes a 62-year-old man presenting with exertional dyspnoea and hypertension. It describes an early misdiagnosis of hypertrophic cardiomyopathy and highlights that clinicians should be alerted in cases of very high left ventricular outflow gradients in the presence of eccentric mitral regurgitation (MR). Here the MR was caused by a rare congenital deformity whereby a deep cleft in the posterior leaflet resulted in a tricuspid appearance. We present the natural disease course of a trileaflet mitral valve and without intervention over 13 years from symptom onset to the development of severe MR.

Background

Trileaflet mitral valves were first described as recently as 2010 by Irwin et al.¹ Although exceedingly rare, improvements in cardiac imaging technologies have led to the increasing characterisation of these congenital phenomena with now nine cases published globally to date.² Of these cases, half describe an association with hypertrophic cardiomyopathy (HCM).^{1 3–6} Only Guerreiro et al ⁷ address the prognostic implication of having trileaflet mitral valve by describing valve function over 10 years with deterioration to severe mitral regurgitation (MR). Given that the corpus of literature available is sparse, we feel this case offers an invaluable opportunity to characterise this condition further including its associations and prognosis.

Case presentation

In 2002, a 62-year-old man with a background of hypertension, hyperlipidaemia and impaired glucose tolerance was referred from primary care with mild exertional dyspnoea, New York Heart Association 2, causing no significant limitation to his activities of daily living. On examination, he was noted to be have a loud apical ejection systolic murmur, retrospectively noted as far back as 1984, as well as being consistently hypertensive recorded as far back as 1981. An ECG showed sinus rhythm with left atrial prominence with right bundle branch block noted to be new since his last ECG in 1993.

Investigations

Two-dimensional (2D) transthoracic echocardiography undertaken on a GE Vivid 3 showed normal mitral valve leaflets with trivial MR and an anteriorly directed jet. There was marked systolic anterior motion of a portion of the anterior leaflet and related subvalvular structures. The left atrium was dilated (5.9 cm). The left ventricle (LV) was not dilated and systolic wall movement was vigorous. LV end-diastolic diameter was 4.4 cm and LV end-systolic diameter was 2.6 cm. There was moderate LV hypertrophy with a posterior wall thickness of 12 mm. The aortic root was not dilated at 3.2 cm. The aortic valve (AV) leaflets appeared normal. There was turbulent colour flow within the LV outflow tract with marked variation in the estimated gradient depending on transducer angulation. An early peaking jet, appreciated to be not typical for HCM at the time, gave a systolic pressure gradient varying from 78 to 130 mm Hg. The right heart chambers were mildly dilated. The findings were concluded to be consistent with HCM without marked septal thickening, but with unusually significant LV outflow gradient, and he was planned for routine outpatient follow-up.

Outcome and follow-up

He was next seen 5 years later in 2007 with a reduction in his exercise capacity to 100 m. An exercise test was undertaken with only 2 min of the Bruce protocol tolerated. A repeat transthoracic echocardiogram showed progression to moderate MR and no other structural or functional change. The m-mode intracavitary pressure gradient was non-classical in that the AV gradient was linear (figure 1). He was referred for assessment of alcohol septal ablation at which point the interventional team opted for medical treatment. A year later in 2008, he developed paroxysmal atrial fibrillation. In 2012, he developed heart failure, severe MR and pulmonary hypertension without significant change to systolic anterior motion, LV hypertrophy or outflow gradient. He was again asked to consider alcohol septal ablation or mitral valve replacement but declined. In 2015, during routine outpatient follow-up, he had a change of heart. This man underwent a repeat 2D echocardiogram with a newer GE Vivid E95 machine for preoperative evaluation that was able to characterise a distinct cleft in the posterior mitral valve leaflet (video 1) accompanied by modest anterior leaflet prolapse, confirmed by 3D echocardiography reconstruction (figures 2 and 3, video 2). The apical four-chamber view shows a morphologically normal RV excluding a congenitally corrected transposition of the great arteries (video 3). Doppler assessment shows an associated complex MR (figure 4, video 4). The images show two papillary muscles in a typical location, though the anteriomedial papillary muscle is divided into two distinct heads(figures 5 and 6). In addition, there is an aberrant chordal insertion noted running from the anterolateral papillary muscle to the interventricular septum (figure 6 and video 5). He later declined intervention. Subsequently, the patient has been offered an experimental mitral clip, where there have been a number of case reports of successful intervention leading to improvement in 2D echocardiographic regurgitation severity, but again declined.^8–10

Figure 1.

LVOT M-mode showing non-classical sabre toothed pattern. LVOT, left ventricular outflow tract.

Video 1.

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DOI: 10.1136/bcr-2018-229106.video01

2D echo short axis illustrating a trileaflet mitral valve.

Figure 2.

3D echo of closed trileaflet mitral valve.

Figure 3.

3D echo of open trileaflet mitral valve.

Video 2.

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DOI: 10.1136/bcr-2018-229106.video02

3D echo illustrating a trileaflet mitral valve

Video 3.

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DOI: 10.1136/bcr-2018-229106.video03

2D apical four-chamber view.

Figure 4.

2D echo five chamber showing complexity of mitral regurgitation.

Video 4.

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DOI: 10.1136/bcr-2018-229106.video04

2D with Doppler showing complexity of mitral regurgitation.

Figure 5.

2D echo long axis showing borderline LVH and papillary muscle position. LVH, left ventricular hypertrophy.

Figure 6.

2D echo short axis showing anteriomedial papillary muscle divided into two distinct heads.

Video 5.

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DOI: 10.1136/bcr-2018-229106.video05

2D echo short axis showing the papillary muscle position.

Discussion

The clinical course of this patient’s trileaflet mitral valve dysfunction is of a systolic murmur at an early age, dyspnoea onset at age 62 and severe valvular dysfunction with pulmonary hypertension at 75. Thirteen years from symptom onset to valve dysfunction is reasonably concordant with the case identified by Guerreiro et al ⁷ where severe valve dysfunction is described to occur at 10 years.

This case demonstrates technological advancement in cardiac imaging during the lifetime of this patient leading to better characterisation of their underlying structural heart disease. Although an association between HCM and trileaflet mitral valves has been described previously, in this case, the early diagnosis of HCM that later did not demonstrate progression of LV hypertrophy or increase in outflow gradient over 16 years was clearly a mischaracterisation of concurrent hypertensive cardiomyopathy with a complex, eccentric MR jet caused by the trileaflet mitral valve that was able to mascaraed as LV outflow obstruction on continuous wave Doppler(figures 1 and 7).^{1 3–6} Interestingly, the patient’s first echocardiogram in 2002 was reported as an unusually significant LV outflow gradient given the minimal degree of LV hypertrophy. It is therefore important in cases of suspected HCM where there is a very high left ventricular outflow gradient in the presence of an eccentric MR jet that clinicians consider a differential diagnosis of a trileaflet mitral valve.

Figure 7.

MR M-mode. MR, mitral regurgitation.

Patient’s perspective.

During my childhood medical practitioners often commented on a loud heart murmur but never explained the significance of it. During this time, I played all types of sport but my exercise tolerance was less than my peers when undertaking long distance running. In my early 40s, I was referred to a cardiologist with hypertension. He had an early version of an echocardiogram and described a ‘lump’ on the septal wall of the left ventricle which was directing a stream of blood flow towards the mitral valve.

In my early 60s, the shortness of breath on exercise became more evident and a suggestion was made that alcohol ablation of the ‘lump’ to cause an infarction, and some reduction in its size, might give some improvement to my situation. Given the reasonable quality of life I then enjoyed together with my new diagnosis of hypertrophic cardiomyopathy would still exist after the procedure, I was tempted to decline the possibility of some improvement with alcohol ablation.

Later in my 60s, I noticed a steady deterioration in my tolerance to exercise and bouts of atrial fibrillation started occurring with congestive heart failure. Sometimes shortness of breath would occur spontaneously when I find it difficult to talk and then only in a whisper, but it passes. I always had to walk slowly and may need to rest for a short time, and I avoid stairs. I have never experienced chest pain.

Following the recent diagnosis of a congenital deformity of the mitral valve, a suggestion that mitral clip insertion may alleviate some of my symptoms. Again I have had to consider the pros and cons of an intervention, however in this case, I feel that my general state of frailty precludes this. The requirement for preoperative investigations, the placement of the clip(s) and the general disruption to life at my present age for an indeterminable benefit seems to me to preclude any intervention at this late stage of the condition. We would still be left with a heart affected by AF and heart failure and some degree of MR. Perhaps nature should be left to take its course.

Learning points.

• In cases of suspected hypertrophic obstructive cardiomyopathy where the intracavity gradient is high and not a classical sabre-toothed profile, clinicians should be aware not to mistake the MR signal for the LV obstruction.

• A trileaflet mitral valve is a rare congenital anomaly, which is associated with early degeneration causing severe MR over a 13-year period from symptom onset.

• Technological advancement in cardiac imaging will likely lead to increased identification of trileaflet mitral valves.