Fifty-two consecutive ambulatory patients (aged 21 to 67 years) with IDCM (New York Heart Association [NYHA] functional class I, II, or III) who underwent both cardiac catheterization and standard polysomnography were enrolled in the study (Fig 1). The diagnosis of IDCM was based on both clinical and histopathologic findings after echocardiography (LV ejection fraction [LVEF] < 45%), coronary angiography, and LV endomyocardial biopsy. Ischemic and primary valvular heart disease were excluded by angiography and echocardiography. Exclusion criteria included a history of alcohol abuse;
Overnight polysomnography was performed according to standard techniques. Breathing variables monitored included chest and abdominal movement, surface intercostal electromyogram, oronasal airflow with thermistor, and airflow using nasal pressure. Apnea, hypopnea, sleep stages, and EEG arousal were scored according to established criteria. Central sleep apnea was defined as the absence of airflow for > 10 s without thoracoabdominal motion and changes in surface intercostal electromyogram, and central hypopnea as a reduction of > 50% in airflow and thoracoabdominal motion from baseline, also for > 10 s without airflow limitation. Central sleep apnea syndrome was defined as the occurrence of > 15 episodes of apnea or hypopnea per hour of sleep (apnea-hypopnea index [AHI]), > 50% of which were determined to be central rather than obstructive. Be safe and sound with My Canadian Pharmacy’s preparations.
Standard echocardiography, including measurement of trans-mitral flow velocity indexes, was performed. LVEF was calculated according to a modification of Simpson method. Mitral regurgitation was graded by color flow Doppler imaging.
LV pressure, pulmonary capillary wedge pressure, and cardiac output were measured. We calculated the peak positive first derivative of LV pressure with respect to time and the pressure half-time.
Treatment With BPAP
The health insurance system in Japan covers the cost of CPAP or BPAP treatment only for individuals with an AHI > 20/h. Study subjects were thus stratified according to the AHI, and those with an index > 20/h were randomly assigned to receive standard medical therapy either alone (11 patients, non-BPAP group) or together with nasal BPAP (10 patients, BPAP group) until the end of the study (Fig 1). BPAP was administered with a BiPAP S instrument (Respironics; Murrysville, PA). On the night after the baseline sleep analysis, those patients assigned to receive BPAP underwent overnight titration of the pressure in order to adjust it to abolish apnea, hypopnea, and oxygen desaturation or to determine the highest level tolerated. Both inspiratory and expiratory pressures were initially set at 4 cm H2O and were increased by 1 cm H2O in a stepwise manner until apnea was eliminated. The expiratory pressure was adjusted to abolish obstructive events. The inspiratory pressure alone was then increased to eliminate hypopnea, oxygen desaturation, snoring, and arousal from sleep. Urine samples were obtained on the two consecutive days involving overnight sleep analysis both before and during treatment with BPAP. Patients in the BPAP group were sent home with a pressure device and instructed to use it for at least 4 h per night on at least 70% of nights. These patients visited their hospitals once a month, and compliance with the pressure treatment protocol was assessed each month during the study from each individual’s recorded usage of the device. The time and cause of death and BPAP use were ascertained from medical records. Quality of life was assessed with the specific activity scale, both before and after 3 months of treatment with or without BPAP. Physicians who interpreted the polysomnography, cardiac catheterization, and echocardiography data obtained before or after 3 months of treatment with or without BPAP were blinded to treatment assignment.
Data are presented as means ± SE. Clinical characteristics were compared between patients with an AHI 20/h with Fisher exact test, the Mann-Whitney U test, or Student unpaired two-tailed t test. Baseline characteristics were compared between the BPAP and non-BPAP groups with Fisher exact test, the Mann-Whitney U test, or Student unpaired two-tailed t test. Parameters at baseline and after treatment with BPAP were compared with Student paired t test. Parameters at baseline were compared between the survivors and nonsurvivors of the non-BPAP group with Student unpaired two-tailed t test. All analyses were performed using statistical software (SPSS 12.0; SPSS; Chicago, IL); p < 0.05 was considered statistically significant.
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Figure 1. Study protocol and subject survival. Mean follow-up time was 31.0 ± 2.3 months.