Aim of the present study was to assess the prevalence of atrial fibrillation (AF) in patients with two different types of cancer. Recent epidemiologic and clinical studies support the hypothesis that AF is promoted and maintained by a broad spectrum of modulating factors. A total of 2,339 patients admitted to the Surgery Department of "Luigi Sacco Hospital, Milan," over the period 1987-2004 were eligible for the study. One thousand three hundred and seventeen patients were admitted consecutively with a first diagnosis of colorectal or breast cancer (cases). The remaining 1,022 were patients admitted to undergo non-neoplastic surgery (controls). Routine pre-surgery electrocardiogram available in patient charts was analysed by a cardiologist who was not aware of the present study to evaluate the presence of atrial fibrillation or other arrhythmias. Overall, AF was present in 3.6% cases and 1.6% controls. This corresponded to at least two times higher likelihood of having AF in cases compared to controls. Prevalence of AF increased with age both in cases and controls. Our study describes an increased prevalence of AF in two different types of cancer. Autonomic, endocrine, coagulation, and inflammatory alterations were previously described in both AF and cancer, and can provide the physiopathological basis to our clinical observation.

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The article by Chung et al 1 reports a significant elevation of C-reactive protein (CRP) in patients with atrial fibrillation (AF). The CRP elevation was found both in patients with lone arrhythmia and in patients with structural heart disease. Moreover, the higher CRP levels were seen in patients with persistent, rather than paroxysmal, AF.We recently conducted a study to quantify the clinical observation of an unexpectedly high frequency of AF in patients with colorectal cancer. 2 We considered a total of 1463 patients admitted to our Department of Surgery from 1987 to 1998 for surgical treatment of colorectal cancer (case group; mean age 66.0 years, 54% males) or nonneoplastic diseases including inguinal hernia, cholelithiasis, varicose veins, and hemorrhoids (control group; mean age 65.6 years, 61% males). We found that atrial fibrillation was three times as likely in patients with first diagnosis of colorectal cancer compared with controls (MantelHaenszel sex-adjusted odds ratioϭ3.5; Cornfield 95% confidence intervalϭ1.6 to 7.2). Logistic analysis was used to exclude an effect of age. All of the patients studied were at the first stage of their diagnosis of colorectal cancer, and they had not received any chemotherapy or previous major surgery.Different pathophysiological mechanisms could explain our observations: a clinical or subclinical hyperthyroidism related to an abnormal release of thyroid-stimulating hormone or T3-like peptides by the tumor; an imbalance between sympathetic and parasympathetic cardiac autonomic control; an autoimmune paraneoplastic syndrome with inflammatory involvement of atrial structures as antigens. 3 Chung et al 1 suggest in their article that AF could be promoted and maintained by atrial structural remodeling because of an inflammatory state, and that elevated CPR may reflect this condition. The cause of the inflammatory state remains unknown. 1 Taking into account the results of our study, the presence of a tumor can sustain systemic inflammation with CPR elevations and could predispose some patients to the development of AF. Moreover, the higher mortality reportedly associated with AF, even after adjustment for preexisting cardiovascular conditions, 4 could be explained in some of these patients by the presence of an inflammatory state due to an occult neoplasm or other systemic inflammatory diseases.

CLS algorithm in a single-chamber device is more effective than AS in detecting an hemodynamic demand due to an emotional stress and supplying a proper HR increase. These results are even more surprising compared to previous data in dual-chamber pacemakers, because they imply that CLS algorithm can provide an appropriate rate-modulation in patients with AF and chronotropic incompetence.