Systemic Vascular Resistance and Myocardial Work Analysis in Hypertrophic Cardiomyopathy and Transthyretin Cardiac Amyloidosis with Preserved Left Ventricular Ejection Fraction

Abstract

Background: The pathophysiological impact of systemic vascular resistance (SVR) and pressure-strain loop-derived global myocardial work index (GWI) in hypertrophic cardiomyopathy (HCM) and transthyretin cardiac amyloidosis (ATTR) has been randomly investigated. Methods: Both SVR and GWI were assessed in outpatients consecutively referred at two Italian cardiology departments for heart failure with preserved left ventricular ejection fraction (LVEF), affected by either nonobstructive HCM or wild-type ATTR. Based on relevant cross-tabulations, the patients were gathered into 4 functional classes according to cut-off values of 1440 dyne/s/cm^-5 for SVR, and 1576 mm Hg% for GWI, as suggested by previous studies. Results: A total of 60 patients, 30 in each group, aged 61 ± 16 years, with 78% males, were studied. HCM patients were younger than those with ATTR and in a better clinical condition (23% HCM vs. 77% ATTR were NYHA class II-III, p < 0.001). Overall, 51 patients (85%) showed a high SVR, 21/30 HCM (70%), and 30 ATTR (100%) (p < 0.005). Both SVR and GWI (expressions of ventricular-arterial coupling) were impaired in 43% of HCM patients (showing greater LV concentric hypertrophy) and 93% of ATTR patients (in advanced NYHA functional class) (p < 0.001). Conclusions: A substantial percentage of present study population showed impaired SVR and/or GWI, despite preserved LVEF. The proposed classification may shed further light on the pathophysiological and clinical characteristics of such hypertrophic phenotypes.

Keywords: cardiac amyloidosis; heart failure with preserved left ventricular ejection fraction; hypertrophic cardiomyopathy; strain echocardiography; systemic vascular resistance; ventricular arterial coupling.

Figure 2

Scatter plot diagram showing four classes categorized according to SVR_c (cut-off 1440 dyne/cm/s⁻⁵) [3,8] and GWI (cut-off 1576 mm Hg%) [18]. Therefore, Class A included patients with low/normal SVRc and preserved GWI, then interpreted as the best functional class. Class B included patients with lower GWI and normal SVR_c, taken as intermediate risk class. Class C included patients with higher SVR_c and impaired GWI, then considered as the worst one. Class D, another intermediate class due to high SVR_c. Vertical dashed lines indicate the cut-off values by previous studies for impaired myocardial perfusion and late gadolinium enhancement (LGE) in HCM patients [21], and major cardiovascular events (MACE) in ATTR patients [22]. Tabulation below the graphics refers to some clinical findings from the patients belonging to different Classes (see also Table 3). ATTRwt, wild-type transthyretin cardiac amyloidosis; HCM, nonobstructive hypertrophic cardiomyopathy; NYHA, New York Heart Association functional class; NSVT, nonsustained ventricular tachycardia on 24-h ECG Holter monitoring; PAF, paroxysmal atrial fibrillation.

Figure 1

Median values of global myocardial constructive work (GCW), global work index (GWI) and systemic vascular resistance (SVRc) in the study population. ATTR, wild-type transthyretin amyloid cardiomyopathy HCM, hypertrophic cardiomyopathy; SVRc, systemic vascular resistance, corrected (see methods). HCM vs. ATTR: * p = 0.008; # p = 0.001. Differences in SVRc between the groups were significant (p = 0.008).