Cardiovascular and health cost impacts of cuff blood pressure underestimation and overestimation of invasive aortic systolic blood pressure

Abstract

Objective: Hypertension management is directed by cuff blood pressure (BP), but this may be inaccurate, potentially influencing cardiovascular disease (CVD) events and health costs. This study aimed to determine the impact on CVD events and related costs of the differences between cuff and invasive SBP.

Methods: Microsimulations based on Markov modelling over one year were used to determine the differences in the number of CVD events (myocardial infarction or coronary death, stroke, atrial fibrillation or heart failure) predicted by Framingham risk and total CVD health costs based on cuff SBP compared with invasive (aortic) SBP. Modelling was based on international consortium data from 1678 participants undergoing cardiac catheterization and 30 separate studies. Cuff underestimation and overestimation were defined as cuff SBP less than invasive SBP and cuff SBP greater than invasive SBP, respectively.

Results: The proportion of people with cuff SBP underestimation versus overestimation progressively increased as SBP increased. This reached a maximum ratio of 16 : 1 in people with hypertension grades II and III. Both the number of CVD events missed (predominantly stroke, coronary death and myocardial infarction) and associated health costs increased stepwise across levels of SBP control, as cuff SBP underestimation increased. The maximum number of CVD events potentially missed (11.8/1000 patients) and highest costs ($241 300 USD/1000 patients) were seen in people with hypertension grades II and III and with at least 15 mmHg of cuff SBP underestimation.

Conclusion: Cuff SBP underestimation can result in potentially preventable CVD events being missed and major increases in health costs. These issues could be remedied with improved cuff SBP accuracy.

Figure 1

Structure of the simulation model. Shown is the microsimulation model to estimate first cardiovascular events (coronary heart disease, stroke, atrial fibrillation, and heart failure) and related costs of acute events, of cuff SBP value versus invasive SBP value in adults who were eligible to participate. ‘M’ designates the Markov node with the different branches indicating the health states in one-year time. The black filled circle indicates the chance node after which there is a probability of having a cardiovascular event. The triangles specify the terminal nodes or the end of the pathway within a one-year cycle. There is only one outcome option per participant per cycle. Invasive SBP is the measured intra-arterial aortic SBP. CVD, cardiovascular disease.

Figure 2

Ratio of the number of people with cuff underestimation versus overestimation across BP classification thresholds (based on invasive aortic SBP). The ratio underestimation versus overestimation was calculated as the number of people with underestimation of BP by cuff SBP as numerator and the number of people with overestimation of SBP by cuff SBP as the denominator. The level of underestimation or overestimation was calculated as the absolute difference between invasive SBP and cuff SBP. BP, blood pressure. Definitions: underestimation: invasive SBP > cuff SBP; overestimation: invasive SBP < cuff SBP; optimal SBP: invasive SBP < 120 mmHg; Normal SBP: invasive SBP ≥120 mmHg and <130 mmHg; high normal SBP: invasive -SBP ≥130 mmHg and <140 mmHg; hypertension I: invasive SBP ≥140 mmHg and <160 mmHg; hypertension II: invasive SBP ≥160 mmHg and <180 mmHg; hypertension III: invasive SBP ≥180 mmHg.

Figure 3

Number of potentially preventable total cardiovascular disease events missed because of cuff SBP underestimation. The difference in the number of total CVD events was calculated as the number of total CVD events with invasive SBP minus the number of CVD events with cuff SBP. The absolute difference between cuff SBP and invasive SBP was calculated as invasive SBP minus cuff SBP. CVD, cardiovascular disease. Definitions: underestimation: cuff SBP < invasive SBP; Optimal SBP: invasive SBP < 120 mmHg; Normal SBP: invasive SBP ≥120 mmHg and <130 mmHg; High normal SBP: invasive SBP ≥130 mmHg and <140 mmHg; hypertension I: invasive SBP ≥140 mmHg and <160 mmHg; Hypertension II: invasive SBP ≥160 mmHg and <180 mmHg; Hypertension III: invasive SBP ≥180 mmHg.

Figure 4

Costs (in USD) of the potentially preventable cardiovascular events missed because of cuff SBP underestimation. The difference in costs (per thousand USD) was calculated as the cost of total CVD events with invasive SBP minus the cost of total CVD events with cuff SBP. The absolute difference between cuff SBP and invasive SBP was calculated as invasive SBP minus cuff SBP. CVD, cardiovascular disease. Definitions: underestimation: invasive SBP > cuff SBP; optimal SBP: invasive SBP <120 mmHg; normal SBP: invasive SBP ≥120 mmHg and <130 mmHg; High normal SBP: invasive SBP ≥130 mmHg and <140 mmHg; hypertension I: invasive SBP ≥140 mmHg and <160 mmHg; hypertension II: invasive SBP ≥160 mmHg and <180 mmHg; hypertension III: invasive SBP ≥180 mmHg.

Figure 5

Number of potentially preventable specific cardiovascular disease events missed because of cuff SBP underestimation. The difference in the number of specific CVD events was calculated as the number of specific CVD events with invasive SBP minus the number of specific CVD events with cuff SBP. The absolute difference between cuff SBP and invasive SBP was calculated as invasive SBP minus cuff SBP. AF: atrial fibrillation; CHD: coronary heart disease; CVD, cardiovascular disease; HF: heart failure. Definitions: underestimation: invasive SBP > cuff SBP; optimal SBP: invasive SBP < 120 mmHg; normal SBP: invasive SBP ≥120 mmHg and <130 mmHg; high normal SBP: invasive SBP ≥130 mmHg and <140 mmHg; hypertension I: invasive SBP ≥140 mmHg and <160 mmHg; Hypertension II: invasive SBP ≥ 60 mmHg and <180 mmHg; hypertension III: invasive SBP ≥ 180 mmHg.