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Journal Club - ACCORD-BP

by Emily Shohfi on 2020-09-04T09:52:00-04:00 | 0 Comments

Effects of Intensive Blood-Pressure Control in Type 2 Diabetes Mellitus

Also known as the "ACCORD-BP " study, Discussed September 4, 2020


PICO question used:

In patients with diabetes and hypertension, is intensive bloop pressure control more effective  than non-intensive blood pressure control in reducing nonfatal MI, nonfatal stroke, or CV mortality?


Key clinical take-aways from this article: 

  • Why we should know it:  In patients with T2DM at high risk for CV events, targeting SBP <120 mmHg did not reduce rates of nonfatal MI, nonfatal stroke, or CV mortality when compared to a target SBP <140 mmHg.

    • Intensive BP control did not significantly reduce the primary cardiovascular outcome or the rate of death from any cause, nor most of the secondary trial outcomes (at p<0.05, intensive BP management did not reduce rate of total stroke or nonfatal stroke) despite the fact that there was a significant and sustained difference between the intensive-therapy group and the standard-therapy group in mean systolic blood pressure

  • Overview: 77 sites with 10,000 patients in the US split into 3 groups - the ACCORD-Glycemia (A1c), ACCORD-BP, and the ACCORD-Lipid trials. Controlled BP in type two diabetics for <120 or <140 in two groups, looking at nonfatal MI, nonfatal stroke, or death from cardiovascular causes. They followed up for ~5years.

  • People in this study were approximately 62, 47% female, 8-9 years into their disease course (would catching them earlier have made a difference to study results?), 34% prior CVD, and not many Hispanics included in the study.  
  • Intensive BP didn't reduce their risk; the standard therapy was expected to have a much higher event rate, but perhaps the patients were healthier than they may have normally been because the sickest of the trials' participants were shunted into the ACCORD-Lipid trial 
  • BP Goals were a little different than they are today because it was prior to new guidance; guidance today, especially from JNC-7 for diabetics, is <130, and 125-130 for diabetics. 
    • Discuss - could we consider <130/80 in patients with diabetes unnecessary since <130/70 did not confer benefit compared to <140/90

Shortcomings 

  • Open Label
  • Likely underpowered
    • event rate in the conservative therapy group was half of that anticipated
    • this lower than expected rate may have reduced the study's power to demonstrate significant findings
  • demographics not entirely representative
  • Confounding
    • Duration of the study was 4.7 years - might require more time to see difference between arms of the study
    • groups treated slightly differently - could effect results

Statistics discussed

  • Confounding
  • Bias
  • Power
  • Clinical/Statistical Significance

  • Other notes: Hazard Ratio vs RRR

    • What's the difference? - HR and RR are often interpreted similarly, but they're not technically the same. One of the biggest differences between the two is that the risk ratio doesn't care about the timing of the event - only about the occurrence of the event by the end of the study ( if it happened or not; the total number of events by the end of the study period)
    • In contrast, hazard ratios look at both the total number of events AND the timing of that event
    • It's good to think about hazard ratios as how long it will take for a particular event/outcome to occur, and what the risk is of something happening in the next moment.
      • They represent hte instantaneous event rate (the probability that an individual would experience an event such as death or relapse) at a particular point in time after the intervention given that they've survived until that point. 
      • You'll often see these accompanied by Kaplan-Meier curves to visually represent them. 
  • Looking at the numbers:
  • 1 is our equal event rate number: when the HR = 1, the event rate is the same in both the treatment and control groups
  • <1 ; the treatment group is faring better than the control. For example, HR = 0.5, half as many patients in the treatment group are experiencing an event compared to the control group
  • >1 ; the treatment group isn't doing so hot. For example, HR = 2, twice as many patients in the treatment group are experiencing an event compared to the control group. 
    • When looking at HR, make sure you also check to see if they p value is significant (<0.05). 

Guidelines

  • led to the JNC 8 (2013) BP targets diabetics to increase to <140/90 mm Hg

2017 ACC AHA AAPA ABC ACPM AGS APhA ASH ASPC NMA PCNA Hypertension (2017, adapted)

  • New definitions for BP ranges: Normal BP is <120/<80, elevated BP is 120-129/<80, stage 1 HTN is 130-139/80-89, and stage 2 HTN is ≥140/≥90 mm Hg
  • First line agents include thiazide diuretics (chlorthalidone preferred), CCBs, and ACE-inhibitors or ARBs (COR I, LOE A)
  • For diabetics, treat to BP goal <130/80 mm Hg (COR I, LOE B-R for SBP and C-EO for DBP)
    • Any first-line medication is effective (COR I, LOE A), but consider ACE-inhibitors and ARBs if albuminuria (COR IIb, LOE B-NR)


Citation

ACCORD Study Group. "Effects of intensive blood-pressure control in type 2 diabetes mellitus". The New England Journal of Medicine. 2010. 362(17):1575-1585.

https://www.ncbi.nlm.nih.gov/pubmed/20228401


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