Aortic root dimensions are predominantly determined by genetic factors: a classical twin study

Valvular Heart Disease Epidemiology

Valvular heart disease is a rapidly growing cause of global cardiovascular morbidity and mortality with diverse and evolving geographic distribution. The prevalence of rheumatic heart disease, the most common valvular heart disease (affecting approximately 41 million people), has been rising in developing nations, likely due to the expansion of the young adult population and the decrease in premature mortality that has resulted from improved access to antibiotics, microbiological testing, and echocardiography. Rheumatic heart disease has also been rising among the impoverished and, often, indigenous populations of developed nations, spurring public health initiatives that are aimed at alleviating healthcare disparities. Aortic valve stenotic disease is the most commonly occurring valvular pathology in developed nations (afflicting 9 million people worldwide) and its prevalence has been increasing with population aging and the increased prevalence of atherosclerosis. Aortic regurgitation is associated with diastolic, but not systolic, hypertension and it has likewise seen a rise in the developed world. Mitral regurgitation affects 24 million people worldwide, with great variability between and among nations. Primary mitral regurgitation arises as a consequence of myxomatous degeneration and mitral valve prolapse, which is largely due to genetic predispositions, while secondary mitral regurgitation accounts for 65% of cases and arises secondary to dilation and heart failure. Tricuspid regurgitation has become more prevalent in developed nations due to the increased usage of intracardiac pacemakers. Infective endocarditis prevalence has also grown in developed nations, likely due to population aging and the increased utilization of transcatheter valve replacement and prosthetic valves as interventions against the previously discussed valvular pathologies.

Genomic insights in ascending aortic size and distensibility

Background

Alterations in the anatomic and biomechanical properties of the ascending aorta (AAo) can give rise to various vascular pathologies. The aim of the current study is to gain additional insights in the biology of the AAo size and function.

Methods

We developed an AI based analysis pipeline for the segmentation of the AAo, and the extraction of AAO parameters. We then performed genome-wide association studies of AAo maximum area, AAo minimum area and AAo distensibility in up to 37,910 individuals from the UK Biobank. Variants that were significantly associated with AAo phenotypes were used as instrumental variables in Mendelian randomization analyses to investigate potential causal relationships with coronary artery disease, myocardial infarction, stroke and aneurysms.

Findings

Genome-wide association studies revealed a total of 107 SNPs in 78 loci. We annotated 101 candidate genes involved in various biological processes, including connective tissue development (THSD4 and COL6A3). Mendelian randomization analyses showed a causal association with aneurysm development, but not with other vascular diseases.

Interpretation

We identified 78 loci that provide insights into mechanisms underlying AAo size and function in the general population and provide genetic evidence for their role in aortic aneurysm development.

Global epidemiology of valvular heart disease

Valvular heart disease (VHD) is a major contributor to loss of physical function, quality of life and longevity. The epidemiology of VHD varies substantially around the world, with a predominance of functional and degenerative disease in high-income countries, and a predominance of rheumatic heart disease in low-income and middle-income countries. Reflecting this distribution, rheumatic heart disease remains by far the most common manifestation of VHD worldwide and affects approximately 41 million people. By contrast, the prevalence of calcific aortic stenosis and degenerative mitral valve disease is 9 and 24 million people, respectively. Despite a reduction in global mortality related to rheumatic heart disease since 1900, the death rate has remained fairly static since 2000. Meanwhile, deaths from calcific aortic stenosis have continued to rise in the past 20 years. Epidemiological data on other important acquired and congenital forms of VHD are limited. An ageing population and advances in therapies make an examination of the changing global epidemiology of VHD crucial for advances in clinical practice and formulation of health policy. In this Review, we discuss the global burden of VHD, geographical variation in the presentation and clinical management, and temporal trends in disease burden.