A new study indicates that long-term exposure to elevated blood pressure is associated with an increased risk of primary and secondary mitral regurgitation. According to investigators Kazem Rahimi (The George Institute for Global Health, University of Oxford, Oxford, UK) and others, this finding implies that blood pressure control may be important for preventing mitral regurgitation.
Writing in PLoS Medicine, Rahimi et al report that despite “substantial progress” in the understanding of the pathophysiology of mitral regurgitation and advances (both surgical and transcatheter) in its treatment, there are no established preventative strategies for the condition. They add that although mitral regurgitation is categorised as primary or secondary, the distinction between these subtypes is “not always obvious and about two thirds of all mitral regurgitation are classified as degenerative”—implying that the condition is a typical consequence of ageing.
The investigators sought to evaluate the role of elevated blood pressure in mitral regurgitation because hypertension correlates with higher left ventricular pressure and “this, in turn, exposes the mitral valve to higher physical stress”; therefore, they add, “it seems plausible that long-term exposure to higher blood pressure could also lead to structural and functional changes of the mitral valve”.
Reviewing data from the UK Clinical Practice Research Database (CPRD), they identified 5,553,894 patients who had at least one blood pressure measurement between 1990 and 2015. Of these, 0.52% were diagnosed with mitral regurgitation during follow-up and 0.02% were diagnosed with mitral stenosis. Rahimi et al note: “When usual systolic blood pressure was analysed as a continuous variable, each 20mmHg increment in usual systolic blood pressure was associated with a 26% higher risk of mitral regurgitation. Compared with a reference category of usual systolic blood pressure of ≤120mmHG, patients with usual systolic blood pressure of ≥161mmHg were 1.5 times more likely to be diagnosed with mitral regurgitation.”
They comment that the risk associated with blood pressure differed with age; patients aged less than 50 years at baseline had 54% higher risk of mitral regurgitation with each 20mmHg increment in usual systolic blood pressure whereas patients aged 71–90 years had a 13% higher risk. Furthermore after adjusting for ischaemic heart disease, myocardial infarction, heart failure, or cardiomyopathy (all of which were strongly associated with mitral regurgitation during follow-up), Rahimi et al found that elevated blood pressure was still associated with a risk of mitral regurgitation (although the risk was mediated). They comment that, following adjustment, 87% of the effect of blood pressure on mitral regurgitation was “independent of the diseases of the left ventricle that occurred during follow-up” and that this suggested that “blood pressure may exert its main effect on the mitral valve directly or via mechanisms unrelated to ventricular dilatation or dysfunction”.
“Our large-scale prospective study suggests that long-term exposure to elevated blood pressure across its whole spectrum is associated with an increased risk of primary and secondary mitral regurgitation. These findings suggest that blood pressure control may be of importance in the prevention of mitral regurgitation.” They add that that “mitral regurgitation is not an inevitable consequence of ageing”.
Study authors Kazem Rahimi and Catherine Otto (University of Washington, Seattle, USA) told Cardiovascular News: “The key message for patients and clinicians is that treating hypertension, particularly in younger adults, may be important to prevent long-term damage to the heart valves.”