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Benefits of CRT less pronounced in HF patients with diabetes
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Although nondiabetic patients with HF benefited more from cardiac resynchronization therapy than their diabetic counterparts, patients with diabetes did experience a significant gain in terms of functional parameters and left ventricular diastolic and systolic function after receiving treatment, researchers reported in Diabetes Care.
The study population included 710 CRT recipients, 171 of whom had diabetes. Performed at baseline and 6-month follow-up were echocardiographic evaluations and LV systolic and diastolic function assessments. Response to CRT was defined as a reduction of ≥15% in LV end-systolic volume at the 6-month follow-up. During a median follow-up of 38 months, the primary endpoint of all-cause mortality and the secondary endpoint of cardiac death or HF hospitalization were recorded.
All elevated parameters improved significantly across all populations within 6 months of the study, according to the researchers. In particular, 371 patients (53%) were classified as responders to CRT. Furthermore, the percentage of mitral regurgitation ≥2 in the studied population decreased significantly as compared with the baseline, from 47% to 32%. Additionally, LV diastolic function improved at 6 months follow-up in the entire patient population.
However, the researchers found that patients without diabetes responded more frequently to CRT than those with diabetes (57% vs. 45%; P<.05). They also found a significant improvement in LV systolic function in both patients with and without diabetes after CRT, but this improvement was more pronounced in patients without diabetes. Improvements in LV diastolic dysfunction were also more pronounced and the long-term outcome after CRT was superior in patients without diabetes. Data identified LV dyssynchrony, ischemic cardiomyopathy and insulin use as determinants of the response to CRT in patients with diabetes.
Study results also showed that the primary and secondary endpoints occurred more often in patients with diabetes compared with those without the disease (P<.001). Diabetes in particular was independently associated with all-cause mortality along with ischemic cardiomyopathy, renal function, LV end-systolic volume, LV dyssynchrony and LV diastolic dysfunction, the researchers wrote.
Disclosure: See the full study for a list of the researchers' relevant financial disclosures.
Perspective
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Frank Smart, MD
First, the study reaffirmed that CRT was beneficial for diabetics and nondiabetics; it prolonged lives and made people feel better. This study also examined echocardiographic parameters that were collected over the course of the 710 CRT patients at baseline and again at 6 months. The investigators looked at various parameters including diastolic and systolic function, and drew conclusions based on whether the patient had diabetes. A limitation of the analysis is that in the study of 710 patients, there was not a large number of patients with insulin-dependent diabetes, (33 or 4.6% of the study population). Second, most of the study participants were men, (75.4%). If you examine diabetes vs. non-diabetes randomization, there are more patients with ischemic etiology and smaller hearts (LVEDVi) in the diabetic group. Case-matched survival is worse in ischemic cardiomyopathy patients. Additionally, if you look at individuals with ischemia, they are going to be less likely to have systolic improvement and have more myocardial scar. Those individuals have a ‘harder hill to climb,’ because ischemic scar never completely goes away. Patients who were nonischemic have a better chance at seeing overall ventricular improvement with any HF therapy, but particularly with CRT.
The study is important because it shows improvement in both patients with and without diabetes. We don’t use CRT to improve an echocardiographic parameter; we use it to improve both survival and exercise parameters, and it seems to work in both of those groups. Regardless of whether a patient has diabetes or not, if there is an indication for CRT then that patient should be treated with CRT. Even though diabetics may not fare as well, they still fare better than diabetic patients with cardiomyopathy who didn’t get the CRT.
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