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Authors' Interview: Paweena Susantitaphong, MD; Bertrand L. Jaber, MD, MS

  • Extracorporeal Multiorgan Support Dialysis Center, Division of Nephrology, Department of Medicine, King Chulalongkorn Memorial Hospital, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand

  • St. Elizabeth's Medical Center, Tufts University School of Medicine, Boston, MA

 

Publication:

Effect of Frequent or Extended Hemodialysis on Cardiovascular Parameters : A Meta-analysis

Paweena Susantitaphong, Ioannis Koulouridis, Ethan M. Balk, Nicolaos E. Madias,
Bertrand L. Jaber
American Journal of Kidney Diseases - 27 February 2012 (10.1053/j.ajkd.2011.12.020)

Study purpose:

Cardiovascular disease is the leading cause of death in hemodialysis (HD) patients, and left ventricular hypertrophy (LVH) is an independent predictor of mortality in this population. Conventional in-center HD (≤ 4 hour session length, thrice weekly) is associated with substantial fluctuations in the extracellular-fluid volume and serum electrolytes. Frequent (2-8 hour session length, > thrice weekly) and extended (> 4 hour session length, thrice weekly) HD might provide better control of the extracellular-fluid volume and blood pressure, and enhance the removal of uremic molecules with cardiac remodeling properties.

This might improve cardiovascular outcomes compared to conventional HD. As a result, we conducted a meta-analysis to examine the potential benefits of frequent or extended HD on cardiac morphology and function, including left ventricular mass index (LVMI), and blood pressure parameters.

What are the main findings of the report?

In single arm studies, we found that frequent or extended HD significantly reduced LVMI from baseline (-31.2 g/m2, 95% CI -39.8,-22.5, P<0.001). Smaller net reductions in LVMI were observed in the few randomized controlled trials. LV ejection fraction improved by 6.7% (95% CI 1.6, 11.9; P=0.01).

Other cardiac morphological parameters displayed similar improvements. There were also significant decreases in systolic (-14.1 mmHg; 95% CI -17.2, -11.0; P<0.001), diastolic (-7.1 mmHg; 95% CI -9.2, -4.9; P<0.001), and mean blood pressure (-11.8 mmHg; 95% CI -13.8, -9.8; P<0.001).

The mean number of anti-hypertensive medications decreased by an average of 0.8 (95% CI -1.2, -0.5; P<0.001), and by the end of the follow up period, 53.5% (95% CI 42.9, 63.8) of patients receiving frequent or extended HD were not taking anti-hypertensive medications. There was no observed benefit on all-cause mortality.

Were any of the findings unexpected?

Most of the findings were expected with a significant improvement in several measures of cardiac morphology, including the LVMI, an important intermediate cardiovascular risk factor.

There was also a significant improvement in the LVEF, an important cardiac functional index, and several blood pressure parameters, including improvements in systolic and diastolic blood pressures, and a decrease in the mean number of anti-hypertensive medications.

An unexpected finding was the improvement in the left atrial end diastolic diameter (LAEDD), which may be of relevance in light of the increasing prevalence of atrial fibrillation in HD patients. A LAEDD of greater than 40 mm predicts development of atrial fibrillation and resistance to medical therapy.

We can only speculate as to whether the left atrial diameter reduction that was observed with frequent or extended HD might result in a lower incidence of atrial fibrillation.

What should clinicians and patients take away from this study?

Strengths of the study include the compilation of a large number of studies, and a demonstrable benefit of frequent or extended HD on all measures of cardiac morphology, cardiac function, and blood pressure parameters.

An important limitation is the paucity of randomized controlled trials, as this meta-analysis primarily evaluated single-arm studies, which might have resulted in a regression-toward-the-mean phenomenon.

Observation bias introduced by the use of blinded vs. non-blinded readers of the cardiac imaging studies is another source of heterogeneity.

We were also unable to address the potential risks associated with frequent HD, including vascular access-related events and hospitalizations.

What recommendations do you have for future studies as a result of your study?

In our meta-analysis of primarily single-arm studies, conversion from conventional thrice-weekly HD to frequent or extended HD is associated with an improvement in cardiac morphology, cardiac function, and blood pressure parameters.

These changes might confer a long-term cardiovascular benefit, calling for the design of large randomized controlled trials of these alternative dialysis regimens with long- term follow up, and aimed at examining cardiovascular morbidity and mortality in this high-risk population.

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