Journey from aortic regurgitation to stenosis - left ventricular structural and perfusion changes seen in patient-prosthesis mismatch

Abstract

Description of Clinical Presentation: A 51 years old lady was referred to Cardiology with a six-month history of breathlessness and reduced exercise tolerance (NYHA 3). Her background includes antiphospholipid syndrome (APLS), hypertension, previous transient ischaemic attacks (TIAs), epilepsy and hypercholesterolaemia. Echocardiography showed severe aortic regurgitation (AR) with a dilated left ventricle (LV) and mildly impaired LV systolic function. She was referred for surgical aortic valve replacement (AVR). Pre-operative CT coronary angiography showed a calcium score of 0 and unobstructed coronary arteries. She underwent an elective surgical AVR (tissue Perimount Magna Ease, 21mm) which was uncomplicated. Post-operatively, she reported increasing breathlessness with associated notable weight gain. Follow-up echocardiography showed increased flow across AVR (Vmax 3.9 m/s, pressure gradient (PG) 37 mmHg, indexed effective orifice area (iEOA) 0.47 cm2/m2). Diagnostic Techniques and Their Most Important Findings: Cardiac magnetic resonance imaging (CMR) was undertaken pre- and post-AVR at 1.5T (Siemens Aera). Pre-AVR CMR showed a severely dilated left ventricle (LV) with severe eccentric hypertrophy, low-normal LV systolic function in the setting of significant AR (Figure 1 and Table 1). Right ventricular size and function was normal with no RV hypertrophy. The atria were normal size. Flow imaging showed severe AR with a Regurgitation Fraction (Reg F) of 46% and resultant increased forward velocity across the valve (3.0 m/s). Late gadolinium enhancement (LGE) demonstrated subendocardial LGE in basal-mid inferolateral wall, patchy mid-wall enhancement in basal-mid inferior, inferolateral wall and septum. Native myocardial T1 (MOLLI) at 1098ms (NR). Diagnostic Techniques and Their Most Important Findings: Cardiac magnetic resonance imaging (CMR) was undertaken pre- and post-AVR at 1.5T (Siemens Aera). Pre-AVR CMR showed a severely dilated left ventricle (LV) with severe eccentric hypertrophy, low-normal LV systolic function in the setting of significant AR (Figure 1 and Table 1). Right ventricular size and function was normal with no RV hypertrophy. The atria were normal size. Flow imaging showed severe AR with a Regurgitation Fraction (Reg F) of 46% and resultant increased forward velocity across the valve (3.0 m/s). Late gadolinium enhancement (LGE) demonstrated subendocardial LGE in basal-mid inferolateral wall, patchy mid-wall enhancement in basal-mid inferior, inferolateral wall and septum. Native myocardial T1 (MOLLI) at 1098ms (NRmax 3.9 m/s). There was notably reduced stress myocardial blood flow circumferentially and globally, not pertaining to a coronary territory and not present pre AVR (Figure 1, bottom right panel). As in pre-AVR, LGE demonstrated a mixed pattern of persistent subendocardial scar in basal-mid inferolateral wall and non-ischaemic mid-wall scar. Learning Points from this Case: These findings represent patient-prosthesis mismatch (PPM) following surgical AVR. Especially interesting is the pattern of subendocardial hypoperfusion at stress, which is usually seen in severe aortic stenosis (AS)1. The mixed pattern of scar is unlikely to be explained by adverse remodelling in AR alone and is most consistent with multiple embolic events (given the absence of coronary artery disease and her history of APLS and previous TIAs). PPM is a recognized finding following valve intervention and severity is graded on iEOA with severe . The mixed pattern of scar is unlikely to be explained by adverse remodelling in AR alone and is most consistent with multiple embolic events (given the absence of coronary artery disease and her history of APLS and previous TIAs). PPM is a recognized finding following valve intervention and severity is graded on iEOA with severe 2/m2 2. It is relatively common with an incidence of up to 54% post-surgical AVR with an increased medium-long term mortality risk3. Risk factors for developing PPM in this case include female sex, hypertension, tissue rather than mechanical AVR (relatively small valve size at 21mm) and significant weight gain post-operatively2. Morphological changes seen on CMR in PPM may appear similar to those of severe AS with a more concentric pattern of hypertrophy, subendocardial hypoperfusion at stress and increased indices of diffuse myocardial fibrosis. Figure 1: Comparison of CMR findings pre-AVR and 6 months post-AVR. Cine: Dilated left ventricle with eccentric hypertrophy pre-AVR versus reduced volumes post-AVR. LGE: Subendocardial enhancement in basal-mid inferolateral wall with patchy mid-wall enhancement in basal-mid inferior, inferolateral wall and septum (pre- and post-AVR). Flow: Significant Regurgitation Fraction of 46% pre-AVR versus 6% post-AVR however increased Vmax post-intervention (3.0 m/s to 3.9 m/s). ECV: Increased post-AVR (33%) [normal 25+/-3%]. Stress MBF: Reduced MBF on stress post-AVR versus pre-AVR. Abbreviations: AVR (Aortic Valve Replacement); ECV (Extracellular Volume); LGE (Late Gadolinium Enhancement); MBF (myocardial Blow Flow); Reg F (Regurgitant Fraction, %); Vmax (maximal velocity across aortic valve, m/s) [Formula presented] Table 1: Comparison of Pre- and Post- intervention CMR Findings (both at 1.5T). Abbreviations: AVR (Aortic Valve Replacement); CMR (Cardiac Magnetic Resonance); LVEDVi (Left Ventricular End Diastolic Volume indexed); LVEF (Left Ventricular Ejection Fraction); LVESVi (Left Ventricular End Systolic Volume indexed) [Formula presented] [Formula presented]