Endomyocardial Biopsy Characterization of Heart Failure With Preserved Ejection Fraction and Prevalence of Cardiac Amyloidosis

Abstract

Objectives: This study prospectively evaluated endomyocardial biopsies in patients with heart failure with preserved ejection fraction (HFpEF) to identify histopathologic phenotypes and their association with clinical characteristics.

Background: Myocardial tissue analysis from a prospectively defined HFpEF cohort reflecting contemporary comorbidities is lacking.

Methods: Patients with HFpEF (EF ≥50%) referred to the Johns Hopkins HFpEF Clinic between August 2014 and September 2018 were enrolled for right heart catheterization and endomyocardial biopsy. Clinical features, echocardiography, hemodynamics, and tissue histology were determined and compared with controls (unused donor hearts) and HF with reduced EF (HFrEF).

Results: Of the 108 patients enrolled, median age was 66 years (25th to 75th percentile: 57 to 74 years), 61% were women, 57% were African American, 62% had a previous HF hospitalization, median systolic blood pressure was 141 mm Hg (25th to 75th percentile: 125 to 162 mm Hg), body mass index (BMI) was 37 kg/m² (25th to 75th percentile: 32 to 45 kg/m²), and 97% were on a loop diuretic. Myocardial fibrosis and myocyte hypertrophy were often present (93% and 88%, respectively); however, mild in 71% with fibrosis and in 52% with hypertrophy. Monocyte infiltration (CD68+ cells/mm²) was greater in patients with HFpEF versus controls (60.4 cells/mm² [25th to 75th percentile: 36.8 to 97.8] vs. 32.1 cells/mm² [25th to 75th percentile: 22.3 to 59.2]; p = 0.02) and correlated with age and renal disease. Cardiac amyloidosis (CA) was diagnosed in 15 (14%) patients (HFpEF-CA: 7 patients with wild-type transthyretin amyloidosis [ATTR], 4 patients with hereditary ATTR, 3 patients with light-chain amyloidosis, and 1 patient with AA (secondary) amyloidosis), of which 7 cases were unsuspected. Patients with HFpEF-CA were older, with lower BMI, higher left ventricular mass index, and higher N-terminal pro-B-type natriuretic peptide and troponin I levels.

Conclusions: In this large, prospective myocardial tissue analysis of HFpEF, myocardial fibrosis and hypertrophy were common, CD68+ inflammation was increased, and CA prevalence was 14%. Tissue analysis in HFpEF might improve precision therapies by identifying relevant myocardial mechanisms.

Keywords: HFpEF; amyloidosis; biopsy; fibrosis; hypertrophy; inflammation.

Figure 1.. Frequency of Histologic Findings on Endomyocardial Biopsy in 108 HFpEF Patients.

Qualitative grading of myocardial fibrosis (Masson’s trichrome) and hypertrophy (Hematoxylin & Eosin) by a cardiovascular pathologist. Cardiac amyloidosis (Congo Red stain) was diagnosed in patients with at least moderate infiltration with amyloid fibrils. HFpEF, heart failure with preserved ejection fraction.

Figure 2.. Representative Histologic Findings on Endomyocardial Biopsies in HFpEF.

A) Interstitial fibrosis (blue) on Masson’s Trichrome stain. B) CD68+ cells (brown) on immunohistochemistry. C) Myocyte hypertrophy on Hematoxylin & Eosin stain. D) Cardiac amyloidosis on Congo Red stain. All images captured at 20x magnification.

Figure 3.. Percent Fibrosis Higher in HFpEF v. Control Tissue, but Lower than HFrEF.

Percent area with fibrosis was analyzed in the Masson’s trichrome stained slides using image analysis platform HALO and slides digitized at 20X. *Non-amyloid HFpEF vs control, p=0.003; **non-amyloid HFpEF vs HFrEF, p=0.03; Wilcoxon test. HFpEF = Heart failure with preserved ejection fraction; HFpEF-CA = HFpEF-cardiac amyloidosis, HFrEF = Heart failure with reduced ejection fraction.

Figure 4.. CD68+ inflammation greater in HFpEF v. control tissue and HFrEF.

CD68+ inflammation was analyzed using image analysis platform HALO and slides digitized at 20X. CD68+ cell number was calculated as number of cells per tissue area in non-amyloid HFpEF, HFpEF-CA, control, and HFrEF tissue. *Non-amyloid HFpEF vs control, p=0.02; non-amyloid HFpEF vs HFpEF-CA, p=0.09; non-amyloid HFpEF vs HFrEF, p=0.0033, Wilcoxon test. HFpEF = Heart failure with preserved ejection fraction; HFpEF-CA = HFpEF-cardiac amyloidosis, HFrEF = Heart failure with reduced ejection fraction.

Figure 5A.. Serum NTproBNP higher in HFpEF-CA v. non-amyloid HFpEF.

Serum N-terminal pro-B-type natriuretic peptide was significantly higher in HFpEF-CA compared to NTproBNP. Natural log transformed values are shown. *p=0.0002, Wilcoxon test. HFpEF = heart failure with preserved ejection fraction; HFpEF-CA = HFpEF-cardiac amyloidosis. NTproBNP = N-terminal pro-B-type natriuretic peptide.

Figure 5B.. Troponin I elevated in HFpEF-CA v Non-Amyloid HFpEF.

Frequency of patients within each range of troponin I. *p<0.0001, Fisher’s exact test. HFpEF = Heart failure with preserved ejection fraction; HFpEF-CA = HFpEF-cardiac amyloidosis.

Central Illustration.. Myocardial Histopathologic Findings and Prevalence in Heart Failure with Preserved Ejection Fraction and Associated Clinical Comorbidities.

Representative histologic images and frequency of findings from 108 HFpEF patients studied are shown for fibrosis (Masson’s trichrome), hypertrophy (Hematoxylin & Eosin), inflammation (CD68 immunohistochemistry), and cardiac amyloidosis (Congo Red stain). CD68+ inflammation was compared to control tissue in n=76 non-amyloid HFpEF patients. *p=0.02 for comparison between CD68+ staining cells in HFpEF v. controls. HFpEF, heart failure with preserved ejection fraction.