Association between the baseline peripheral blood monocyte counts, the size of spleen, and the response to cardiac resynchronization therapy.

Background: Spleen reserves monocytes, which deploy to inflammatory sites. Monocytosis is known to be observed in chronic low-grade inflammatory state, including chronic heart failure (CHF). CHF also induces splenomegaly. We tested the hypotheses that the number of peripheral blood monocytes and size of spleen at baseline could be related to the response to cardiac resynchronization therapy (CRT).

Methods: From 2010, a total of 49 consecutive patients implanted with CRT device were evaluated at baseline and 6-8 months later. The size of spleen was evaluated at baseline by computed tomography. Blood monocyte counts (BMCs) were examined by blood test apparatus.

Results: Patients were categorized as responders (13 female, mean age 69.0±7.9 years, n=34) and nonresponders (2 female, mean age 72.0±8.8 years, n=15) according to echocardiographic findings. In non-responders, spleen index was also greater in non-responders than in responders (4504±1338mm vs. 3240±1115mm; mean±SE, p<0.01). Median baseline BMCs were significantly smaller in responders than non-responders (537±211/μl vs. 336±107/μl, p<0.01). In addition, BMC is positively correlated with the spleen index (R=0.179, p=0.02). Based on the receiver-operating characteristic curve, low BMC was set at <400/μl. Kaplan-Meier survival analysis demonstrated that the low BMC patients had lower prevalence of new hospitalization due to HF progression (log rank 5.35, p=0.02).

Conclusions: Our results demonstrated that BMC and the size of spleen might be important factors for response to CRT.