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Figure.
Blood Pressure Variability
Blood Pressure Variability

A, Slope of blue line: systolic SD = 8.351 + 0.459 × rank; slope of orange line: systolic SD = −26.83 + 2.410 × rank; P = .01; difference in slopes: F1,19 = 67.81; P < .001. B, Slope of blue line: diastolic SD = 4.200 + 0.362 × rank; slope of orange line: diastolic SD = −13.35 + 1.313 × rank; P = .01; difference in slopes: F1,19 = 51.79; P < .001. Dots indicate individual measurements; dotted blue lines indicate the point at which morbidity and mortality risks increase.

Table.  
Demographics, Outcomes, and Blood Pressure Variability
Demographics, Outcomes, and Blood Pressure Variability
1.
Aoyama  R, Takano  H, Suzuki  K,  et al.  The impact of blood pressure variability on coronary plaque vulnerability in stable angina: an analysis using optical coherence tomography.  Coron Artery Dis. 2017;28(3):225-231. doi:10.1097/MCA.0000000000000462PubMedGoogle ScholarCrossref
2.
Chang  TI, Reboussin  DM, Chertow  GM,  et al; SPRINT Research Group*.  Visit-to-visit office blood pressure variability and cardiovascular outcomes in SPRINT (Systolic Blood Pressure Intervention Trial).  Hypertension. 2017;70(4):751-758. doi:10.1161/HYPERTENSIONAHA.117.09788PubMedGoogle ScholarCrossref
3.
Basson  MD, Klug  MG, Hostetter  JE, Wynne  J.  Visit-to-visit variability of blood pressure is associated with hospitalization and mortality in an unselected adult population  [published online May 31, 2018].  Am J Hypertens.PubMedGoogle Scholar
4.
Chung  PJ, Carter  TI, Burack  JH, Tam  S, Alfonso  A, Sugiyama  G.  Predicting the risk of death following coronary artery bypass graft made simple: a retrospective study using the American College of Surgeons National Surgical Quality Improvement Program database.  J Cardiothorac Surg. 2015;10:62. doi:10.1186/s13019-015-0269-yPubMedGoogle ScholarCrossref
5.
Shahian  DM, O’Brien  SM, Filardo  G,  et al; Society of Thoracic Surgeons Quality Measurement Task Force.  The Society of Thoracic Surgeons 2008 cardiac surgery risk models: part 1–coronary artery bypass grafting surgery.  Ann Thorac Surg. 2009;88(1)(suppl):S2-S22. doi:10.1016/j.athoracsur.2009.05.053PubMedGoogle ScholarCrossref
6.
Grassi  G, Bombelli  M, Brambilla  G, Trevano  FQ, Dell’oro  R, Mancia  G.  Total cardiovascular risk, blood pressure variability and adrenergic overdrive in hypertension: evidence, mechanisms and clinical implications.  Curr Hypertens Rep. 2012;14(4):333-338. doi:10.1007/s11906-012-0273-8PubMedGoogle ScholarCrossref
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    Research Letter
    January 2019

    Systolic and Diastolic Blood Pressure Variability as Risk Factors for Adverse Events After Coronary Artery Bypass Grafting

    Author Affiliations
    • 1University of North Dakota School of Medicine and Health Sciences, Grand Forks
    • 2Sanford Health Fargo, Fargo, North Dakota
    JAMA Surg. 2019;154(1):92-94. doi:10.1001/jamasurg.2018.3233

    Although hypertension increases surgical risk, the contribution of chronic outpatient blood pressure variability (BPV) to surgical risk is unclear. Blood pressure variability correlates with altered arterial wall stiffness and atherosclerotic plaque volume and has been associated with subsequent hospitalization, stroke, renal failure, and death.1-3 Patients undergoing coronary artery bypass grafting (CABG) procedures exhibit abnormalities in vascular compliance and endothelial function that predispose them to adverse cardiovascular outcomes.4,5 We hypothesized that long-term, visit-to-visit BPV before surgery is a previously unrecognized risk factor for adverse outcomes after CABG surgery.

    Methods

    We reviewed 21 813 blood pressure recordings from 1334 consecutive patients undergoing isolated CABG surgery between July 2012 and July 2017 at 1 institution. Data were prospectively collected and retrospectively analyzed. Isolated CABG procedures, rather than all patients undergoing cardiac surgery, were studied, because risk factors for isolated CABG surgery are well known and because this approach ensured a more homogenous patient population. We defined BPV as the SD in systolic or diastolic blood pressures between patient encounters, requiring at least 10 preoperative blood pressure measurements up to 3 years before the date of surgery, using a methodology that we and others have previously used for nonsurgical outpatients.1-3

    The Sanford and University of North Dakota institutional review boards approved this study. The requirement for informed consent was waived.

    Outcomes of death, renal failure, stroke, and combined major morbidity and mortality were predefined with Society of Thoracic Surgeons (STS) definitions. Patients’ predefined operative risk for mortality was calculated using the STS Risk Score, and the influence of BPV on outcomes was assessed with and without risk adjustment using the STS Risk Score. The association between preoperative BPV and outcomes after CABG surgery was explored using rank-order analysis and analysis of covariance for testing the equality of slopes.

    Results

    A total of 405 patients met inclusion criteria. The Table details preoperative patient characteristics. The Figure shows the association between the rank and the value of the BPV as a way of identifying a place where the BPV associations suddenly change by sharply increasing. For systolic SD, this is at an SD rank of approximately 17 and for diastolic SD, approximately 18. This suggests but does not define a cutoff value for the BPV that affects patient outcomes.

    Greater diastolic and systolic BPV correlated with increased event rates of combined major morbidity and mortality. After risk adjustment for the STS Risk Score, diastolic BPV remained independently associated with combined major morbidity and mortality (odds ratio [OR], 1.15 [95% CI, 1.01-1.32]; P = .04). Risk-adjusted systolic BPV was associated with renal failure after CABG surgery (OR, 1.14 [95% CI, 1.02-1.28]; P = .02), and a nonsignificant value was obtained for the association of systolic BPV and combined morbidity and mortality (OR, 1.07 [95% CI, 0.99-1.166]; P = .09).

    Discussion

    Preoperative diastolic BPV was found to be an independent risk factor for predefined combined morbidity and mortality before and after risk adjustment. Additionally, the significant change in the slope of the rank-order analysis indicates that higher levels of both systolic and diastolic BPV are significantly more likely to be associated with adverse outcomes, suggesting a threshold level of variability that may be important (Figure). Systolic BPV was also associated with renal failure after CABG surgery, which is common and associated with significant long-term adverse sequelae. Larger data sets will be needed to confirm the association of systolic variability with patient outcomes and more precisely define the threshold or proportionality of BPV that puts patients at risk.

    The mechanism by which BPV affects outcomes is unclear. Long-term BPV increases atherosclerotic plaque vulnerability.1 While this study addressed only patients undergoing CABG surgery, patients with BPV and coronary artery disease undergoing other procedures might also be at increased risk for perioperative complications. In addition, BPV may be a marker for medication noncompliance,6 which may affect surgical outcomes, as nonadherence to secondary prevention is known to adversely affect outcomes. Future studies requiring larger patient populations may address the role of this and other potential confounders. Diastolic and systolic BPV are calculated variables easily flagged within an electronic medical record. Recognition of high BPV may permit additional risk stratification that is clinically useful and easily quantified for patients undergoing CABG procedures.

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    Article Information

    Corresponding Author: Marc D. Basson, MD, PhD, MBA, University of North Dakota School of Medicine & Health Sciences, 1301 N Columbia Rd, Stop 9037, Grand Forks, ND 58202 (marc.basson@med.und.edu).

    Published Online: October 3, 2018. doi:10.1001/jamasurg.2018.3233

    Author Contributions: Dr Basson had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

    Concept and design: Dyke, Klug, Basson.

    Acquisition, analysis, or interpretation of data: Benz, Taggart, Klug, Basson.

    Drafting of the manuscript: Dyke, Klug, Basson.

    Critical revision of the manuscript for important intellectual content: Benz, Taggart, Klug, Basson.

    Statistical analysis: Dyke, Benz, Klug, Basson.

    Administrative, technical, or material support: Basson.

    Supervision: Dyke, Basson.

    Conflict of Interest Disclosures: None reported.

    References
    1.
    Aoyama  R, Takano  H, Suzuki  K,  et al.  The impact of blood pressure variability on coronary plaque vulnerability in stable angina: an analysis using optical coherence tomography.  Coron Artery Dis. 2017;28(3):225-231. doi:10.1097/MCA.0000000000000462PubMedGoogle ScholarCrossref
    2.
    Chang  TI, Reboussin  DM, Chertow  GM,  et al; SPRINT Research Group*.  Visit-to-visit office blood pressure variability and cardiovascular outcomes in SPRINT (Systolic Blood Pressure Intervention Trial).  Hypertension. 2017;70(4):751-758. doi:10.1161/HYPERTENSIONAHA.117.09788PubMedGoogle ScholarCrossref
    3.
    Basson  MD, Klug  MG, Hostetter  JE, Wynne  J.  Visit-to-visit variability of blood pressure is associated with hospitalization and mortality in an unselected adult population  [published online May 31, 2018].  Am J Hypertens.PubMedGoogle Scholar
    4.
    Chung  PJ, Carter  TI, Burack  JH, Tam  S, Alfonso  A, Sugiyama  G.  Predicting the risk of death following coronary artery bypass graft made simple: a retrospective study using the American College of Surgeons National Surgical Quality Improvement Program database.  J Cardiothorac Surg. 2015;10:62. doi:10.1186/s13019-015-0269-yPubMedGoogle ScholarCrossref
    5.
    Shahian  DM, O’Brien  SM, Filardo  G,  et al; Society of Thoracic Surgeons Quality Measurement Task Force.  The Society of Thoracic Surgeons 2008 cardiac surgery risk models: part 1–coronary artery bypass grafting surgery.  Ann Thorac Surg. 2009;88(1)(suppl):S2-S22. doi:10.1016/j.athoracsur.2009.05.053PubMedGoogle ScholarCrossref
    6.
    Grassi  G, Bombelli  M, Brambilla  G, Trevano  FQ, Dell’oro  R, Mancia  G.  Total cardiovascular risk, blood pressure variability and adrenergic overdrive in hypertension: evidence, mechanisms and clinical implications.  Curr Hypertens Rep. 2012;14(4):333-338. doi:10.1007/s11906-012-0273-8PubMedGoogle ScholarCrossref
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