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Importance of Blood Pressure Variability for Stroke Prevention and Management: A Letter to the Editor

To the Editor: I read with great pleasure the article by Santos et al., titled, “Trends in Antihypertensive Medication Use Among Individuals With a History of Stroke and Hypertension, 2005 to 2016” that found uncontrolled blood pressure (BP) in approximately 1 in 3 self-reported stroke survivors and increasing trends in angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (ACEi/ARBs).1 Lack of BP control, however, may be impacted by systolic blood pressure variability (BPV), an increasingly characterized independent predictor of stroke and end-outcomes.2,3 
 
While it is known that acute post-stroke patients may exhibit cardiovascular autonomic dysfunction, there is evidence to suggest BPV also plays a long-term, bi-directional role with stroke, both being a risk factor, independent of mean SBP, as well as a potential consequence.2 Furthermore, antihypertensive medications at this time have limited efficacy in reducing BP variability, with calcium channel blockers (CCBs) showing the most promising results.4 As a result, it is possible that consecutive BP readings may 1) inadequately represent a participant’s 24-hour mean BP, and 2) demonstrate wide variability across readings and thus skew a participant’s mean BP. 
 
Although there are no standardized guidelines for BPV measurement or classification, BPV is most often calculated as the standard deviation of multiple BP readings that are either consecutive (within visit or measurement-to-measurement variability) or across multiple visits (visit-to-visit variability). Additionally, variability can be pathological, physiological, or artificial. While we can assume that artificial variability (e.g. due to measurement technique) was minimized through quality assurance protocols, the use of all three BPs to derive a mean BP may introduce a ‘White Coat-like Effect’, the idea that initial readings are often elevated and thus should be disregarded in mean calculations.5 
 
Furthermore, prevalence of comorbidities such as Type II diabetes and chronic kidney disease can also increase BPV and further impact prognosis of stroke survivors as per BPV.2,3 These comorbidities may have, in part, played a role in the increase in ACEi/ARB use. 
 
Whether these sources of BP variability would affect the conclusions of the study are difficult to ascertain. The study’s findings that those using CCBs had higher prevalence of uncontrolled BP suggest that BP variability may not be playing a major role. Nonetheless, measurement of BPV and BPV-based interpretation of mean BP may provide an additional opportunity for stroke prevention.