Findings of a retrospective study indicated that atrial fibrillation (AFib) is an independent risk factor associated with pulmonary arterial hypertension (PAH) in patients with obstructive hypertrophic cardiomyopathy (OHCM), (odds ratio [OR] 2.31, 95% CI, P =.042).
Patients with PAH also had an increased risk of AFib incidence (OR 2.24, 95% CI, P =.034). The study findings demonstrate that AFib may exacerbate PAH and PAH may also promote AFib, resulting in a cycle with each feeding into the other.
The authors investigated the risk factors of PAH in addition to the relationship between PAH and AFib in patients with OHCM. Compared with patients who had OHCM without PAH, risk factors in individuals with PAH included female gender (P <.001), older age (P <.001), lower body mass index (BMI) (P =.031), more symptomatic presentation (P =.048), and higher AFib prevalence (P =.001). Patients with PAH also demonstrated significantly larger left atrial diameters, higher left ventricular outflow tract (LVOT) gradients, and moderate to severe mitral and tricuspid valve regurgitations.
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Increased left atrial pressure due to left-sided heart disease stretches the left atrium in a way that creates repolarization dispersion, allowing ectopic triggers to maintain AFib, the authors wrote. Additionally, atrial dysfunction due to AFib increases left atrial pressure, resulting in exacerbated PAH.
Clinical Relevance
The clinical relevance of this study, published in Frontiers of Cardiovascular Medicine, is to aid clinicians’ early identification of clinical characteristics which are risk factors associated with PAH development in the context of OHCM. Using the clinical characteristics found in this study, clinicians can diagnose earlier and prescribe treatment to relieve the left ventricular outflow gradient in patients with OHCM. In turn, this lowers the risk of developing PAH by improving left ventricular function and offloading the pressure on the left atrium.
“Early and timely diagnosis and appropriate treatments will reduce PAH in OHCM patients and will eventually improve patient symptoms and long-term prognosis,” the authors wrote.
Methods
Nie et al enrolled 483 patients diagnosed with OHCM at Fuwai Hospital in Beijing, China between January 2015 and December 2017 into this study. They subdivided these patients into those with (n=82) and those without (n=401) PAH based on the pulmonary arterial systolic pressure upon initial examination.
Investigators made the official diagnosis of AFib following examination of clinical data via medical records and in-hospital 12-lead transthoracic echocardiography. They also confirmed PAH using tricuspid valve regurgitation jet velocity to diagnose 79 patients and using peak pulmonary valve regurgitation velocity to diagnose 3 patients.
Limitations
Limitations included the small sample size of patients diagnosed with PAH and the lack of ability to collect data since the study was retrospective in nature. Therefore, researchers were unable to study the right atrial diameter, the main pulmonary arterial diameter, the degree of fibrosis of the right atrium, and the electric remolding of the right atrium. This retrospective hindrance limited the authors’ ability to indicate how PAH was directly involved in AFib development.
Lastly, the gold standard used to diagnose PAH most accurately is right heart catheterization, not echocardiography, the method used in this study.
Reference
Nie C, Zhu C, Xiao M, et al. Risk factors of pulmonary arterial hypertension and its relationship with atrial fibrillation in patients with obstructive hypertrophic cardiomyopathy. Front Cardiovasc Med. Published online July 7, 2021. doi:10.3389/fcvm.2021.666431
