Evaluation of late atrial enhancement by cardiac magnetic resonance imaging in patients with obstructive sleep apnea.

INTRODUCTION: Atrial fibrillation (AF) is a growing public health problem especially due to its association with thromboembolic phenomena. Among its risk factors, obstructive sleep apnea (OSA) has increased in incidence and is often under diagnosed. OSA increases the risk of AF by mechanisms not fully known, but it may lead to remodeling and structural alteration of the atria. Cardiac magnetic resonance (CMR), in addition to assessing heart morphology, allows the identification of areas of fibrosis, including the atrium, by the late gadolinium enhancement technique (LGE) and could identify cases of OSA with potential atrial instability. OBJECTIVE: To evaluate the relationship of LGE atrial by CMR in patients with atrial fibrillation with OSA. METHODS: We selected 81 patients who were divided into four groups: Group 1: 20 OSA patients without AF, Group 2: 20 OSA and AF patients, Group 3: 21 patients with only atrial fibrillation without OSA and Group 4: 20 healthy patients without associated comorbidities. All underwent CMR for morphofunctional evaluation and LGE research. RESULTS: The average age was 57.1+-10.59 years. Clinical variables such as hypertension (p = 0.24) and Diabetes Mellitus (p = 0.20) were not predictors of AF in OSA patients. Of the 40 cases with OSA, 18, 45% had severe obstructive disorder, and in this group AF was more prevalent. The mean left ventricular ejection fraction was 62.9% (+-7.46) and it did not differ between groups (p = 0.2). Patients with concomitant OSA and AF had significantly larger left atria (p < 0.001). Cases of OSA with AF showed significantly more atrial LGE (95% vs. 30%, p < 0.001), being an independent predictor in multivariate analysis (P < 0,001). CONCLUSION: Atrial LGE is independently associated with the presence of AF in patients with OSA. These elements may help to identify cases of higher risk for developing AF in OSA patients in clinical practice.

Depressed cardiac autonomic modulation in patients with chronic kidney disease.

INTRODUCTION: A dysfunctional autonomic nervous system (ANS) has also been recognized as an important mechanism contributing to the poor outcome in CKD patients, with several studies reporting a reduction in heart rate variability (HRV). OBJECTIVE: Evaluate the sympathovagal balance in patients with chronic kidney disease on conservative treatment. METHODS: In a cross-sectional study, patients with CKD stages 3, 4 and 5 not yet on dialysis (CKD group) and age-matched healthy subjects (CON group) underwent continuous heart rate recording during two twenty-minute periods in the supine position (pre-inclined), followed by passive postural inclination at 70° (inclined period). Power spectral analysis of the heart rate variability was used to assess the normalized low frequency (LFnu), indicative of sympathetic activity, and the normalized high frequency (HFnu), indicative of parasympathetic activity. The LFnu/HFnu ratio represented sympathovagal balance. RESULTS: After tilting, CKD patients had lower sympathetic activity, higher parasympathetic activity, and lower sympathovagal balance than patients in the CON group. Compared to patients in stage 3, patients in stage 5 had a lower LFnu/HFnu ratio, suggesting a more pronounced impairment of sympathovagal balance as the disease progresses. CONCLUSION: CKD patients not yet on dialysis have reduced HRV, indicating cardiac autonomic dysfunction early in the course of CKD.