Peak time of acute coronary syndrome in patients with sleep disordered breathing.

BACKGROUND: Recently, sleep disordered breathing (SDB) has gained attention in the field of cardiology. Until now, no study describing the relationship between acute coronary syndrome (ACS) and SDB has been carried out in Japan. METHODS: Among ACS patients admitted to our hospital, 44 patients (mean age 60.6+/-13.5 years) who received a portable polysomnography to measure apnea hypopnea index (AHI) were selected for this study. The circadian pattern of ACS onset was studied in 6-h intervals. In addition, all subjects were divided into three groups according to AHI severity (AHI < 5, 5 < or = AHI < 15, and 15 < or = AHI). Then, a comparative study between peak time of ACS and AHI severity was conducted for each group. RESULTS: In the AHI < 5 group, 66.0% patients suffered from ACS between 12:00 h and 18:00 h and 17.0% between 18:00 h and 24:00 h, and a total of 83.0% patients had ACS between 12:00 h and 24:00 h. In the 5 < or = AHI < 15 group, 49.9% patients had ACS between 24:00 h and 06:00 h, 16.7% patients between 06:00 h and 12:00 h. 12:00-18:00 h and 18:00-24:00 h showed no significant difference. All 22 patients in the 15 < or = AHI group suffered from ACS between 24:00 h and 12:00 h. CONCLUSION: The results of this study suggest a possible relationship between SDB and the onset of ACS between midnight to morning.

Relationship between sleep-disordered breathing level and acute onset time of congestive heart failure.

Sleep-disordered breathing (SDB) is frequently observed in patients with congestive heart failure. Recent studies have shown that SDB negatively affects the onset of congestive heart failure; however, no studies have addressed the relationship between the level of SDB and the onset time of acute dyspnea. We hypothesized that SDB affects the acute onset time of dyspnea (AOT) and investigated the relationship between SDB and AOT. We examined 80 patients (mean age, 61.6 years) with congestive heart failure in a clinically stable condition. AOT was divided into 5 time periods (0:00 - 6:00, 6:00 - 12:00, 12:00 - 18:00, 18:00 - 24:00, and unknown). The apnea-hypopnea index (AHI) was obtained based on the results of polysomnography (PSG) to evaluate the severity of SDB. Acute dyspnea occurred in 59 (73.7%) of the 80 patients. When we divided the patients into an AHI < 5 group and an AHI >or= 5 group, there was no significant difference in the AOT; however, a significant difference was observed in those divided into AHI < 20 and AHI >or= 20 groups (P < 0.001). The patients with AHI >or= 20 had more acute dys-pnea between 18:00 - 24:00 and between 0:00 - 6:00 than those with AHI < 20 (32% and 19%, and 4.1% and 4.1%, respectively). Severe SDB patients tended to have acute dyspnea between midnight and dawn. The results suggest SDB might be one of the risk factors of heart failure.

Functional capacity, skeletal muscle strength, and skeletal muscle volume in patients with myocardial infarction.

Previous studies have reported that skeletal muscle strength is closely related to exercise capacity in patients with myocardial infarction (MI). However, none of the previous studies have fully investigated the correlation between exercise capacity and the skeletal muscle volume (MV). Seventy patients with MI underwent symptom-limited cardiopulmonary exercise testing using a treadmill. The MV was evaluated by electrical impedance analysis and the maximal knee extension strength (Peak torque: PT) was measured by a Biodex. The subjects were divided into 2 groups according to the MV (group L, MV < 22 kg; group H, MV > or = 22 kg). The PT was positively and significantly correlated with the peak V(.)O(2) in both the L and H groups (r = 0.70 versus r = 0.71). The MV of the lower limbs was positively correlated with the peak V(.)O(2) in the L group (r = 0.57), but not in the H group. The lower limb MV was positively and significantly correlated with PT in the L group (r = 0.48), but not in the H group. The exercise capacity of patients with MI is thought to depend on both the strength and volume of the skeletal muscle. In MI patients with high muscle volume, exercise capacity was determined by skeletal muscle strength alone.

Health-related quality of life in relation to different levels of disease severity in patients with chronic heart failure.

The purpose of the present study was to compare differences in physiological outcomes and health-related quality of life (HRQOL) in relation to degree of illness in patients with chronic heart failure (CHF) and to compare HRQOL in CHF patients with that of a normal Japanese population. One hundred and twenty-five patients with stable CHF (93 men, 32 women, mean age 63.3 ± 12.4 years) with left ventricular ejection fraction (LVEF) of less than 40% were enrolled in the present study. We used New York Heart Association (NYHA) functional class as an index of degree of illness. In 64 of the 125 patients, physiological outcome measures included peak oxygen uptake (peak O2) and E/CO2 slope. HRQOL was assessed with the medical outcome study short form-36 (SF-36) Japanese version. In addition, SF-36 scores of CHF patients were compared against Japanese standard values. Age and LVEF did not differ according to NYHA functional class. The eight SF-36 subscale scores and peak O2 decreased with increases in the NYHA functional classes, whereas E/CO2 slope increased with increases in NYHA functional class (p<0.05). Of the 8 SF-36 subscales measured in CHF patients, only the bodily pain score attained that of the normal Japanese population. These findings suggest that HRQOL decreases as NYHA functional class increases and other physiological measures worsen. In addition, HRQOL values of CHF patients were low in comparison with standard values of a normal Japanese population.

Efficacy of steroid therapy for pacing failure in a patient with chronic myocarditis.

A 66-year-old man had a progressive increase in the pacing threshold over a one-year period, resulting from chronic myocarditis. Following steroid therapy, the pacing threshold decreased and became stabilized, and was accompanied by a decrease in the serum creatine kinase, cardiac myosin light chains and pro-collagen III peptide values, but cardiac function did not improve. Endocardial biopsy showed that there was no progression in the fibrosis. The pacing failure improved, but the cardiac function did not. It was believed that the steroid therapy suppressed the progression of the inflammation and fibrosis caused by the chronic myocarditis.

[Development of measure for disease-specific quality of life in patients with chronic heart failure].

OBJECTIVES: To develop a measure for disease-specific health-related quality of life in patients with heart failure and examine its reliability and validity. METHODS: One hundred and four patients with stable chronic heart failure (74 males, 30 females, mean age 64.2 +/- 10.0 years) with left ventricular ejection fractions of less than 40% were enrolled in this study. Each patient responded to the Medical Outcomes Study Short Form 36 (SF-36) and a disease specific questionnaire comprising four categories (dyspnea, sleep, appetite and fatigue), each consisting of five to six questions. A stepwise exploratory factor analysis was applied to the disease-specific measure to consider categorical fitness. In 25 of the 104 patients, the data in the questionnaire were compared with peak oxygen uptake, anaerobic threshold, slope of the regression line relating the ventilatory equivalent to carbon dioxide output (VE/VCO2 slope) and peak work rate. Correlations between the questionnaire and eight components of SF-36 were evaluated. RESULTS: The appetite category proved unreliable and was excluded from consideration, so 12 questions were adopted from the other three categories. Cronbach's a values ranged from 0.68 to 0.89 and the coefficients of test-retest were from 0.84 to 0.94, so both internal consistency and reproducibility of these questions were considered excellent. The scores of three categories well reflected the severity of heart failure based in New York Heart Association functional class. The anaerobic threshold (r = 0.53), peak oxygen uptake (r = 0.66), VE/VCO2 slope (r = -0.48) and peak work rate (r = 0.41) correlated with the total score of the 12 questions. The total scores were closely correlated with the eight components of SF-36. CONCLUSIONS: This study suggests that the disease-specific questionnaire is applicable to evaluation of the health-related quality of life in patients with heart failure.

Relationship between impaired chronotropic response, cardiac output during exercise, and exercise tolerance in patients with chronic heart failure.

The present study was undertaken to investigate the relationship between the extent of impaired chronotropic response and cardiac output during exercise, and exercise tolerance in patients with chronic heart failure. The subjects consisted of 24 patients (mean 60.1 +/- 14.0 years) who had mild chronotropic incompetence. Cardiopulmonary exercise testing was performed in all patients, and heart rate (HR), anaerobic threshold (AT), maximum oxygen uptake (peak VO2), slope of the regression line relating the ventilatory equivalent to carbon dioxide output (VE/VCO2 slope), and exercise time were measured. Cardiac output (CO) was measured by a thoracic bioimpedance method and cardiac index (CI) was calculated. Plasma norepinephrine (NE) was measured at rest and immediately after the exercise test. The changes in HR, NE, and CI from the resting state to immediately after exercise were calculated as deltaHR, deltaNE, and deltaCI, respectively. The deltaNE was converted to a logarithmic scale and deltaHR/log deltaNE was used as a parameter of HR response to sympathetic nerve stimulation. The results were as follows: HR and NE in the resting state had no correlation with AT and with peak VO2. DeltaHR/log deltaNE correlated positively with both AT and peak VO2, and negatively with the VE/CO2 slope. DeltaHR/log deltaNE correlated positively with peak CI, %deltaCI, and deltaCI/exercise time. The data suggest that one of the mechanisms of low exercise tolerance in chronic heart failure patients was due to an inadequate increase in CO response against exercise caused by an impaired HR response to increased NE.

[Different effects of exercise training in patients with myocardial infarction with or without diabetes mellitus].

OBJECTIVES: This study investigated whether myocardial infarction patients with diabetes mellitus had lower heart rate reserve to exercise by measuring the increment in heart rate (HR) divided by the increment of norepinephrine (NE) concentration from rest to peak exercise (delta HR/log delta NE). The difference in exercise training effects was also investigated. METHODS: The 148 patients after myocardial infarction were divided into two groups, the DM group (n = 34) and the non-DM group (n = 114). Cardiopulmonary exercise testing was performed in each subject at 1 and 3 months after the onset. Blood samples were taken at rest and immediately after peak exercise, rest brain natriuretic peptide, rest and peak norepinephrine were analyzed. Exercise training was performed from 1 to 3 months after the onset. RESULTS: Resting heart rates were significantly higher in the DM group than in the non-DM group both at 1 and 3 months although peak heart rates were not significantly different. Peak oxygen uptake were lower in the DM group both at 1 and 3 months after onset of myocardial infarction compared to the non-DM group. End-tidal carbon dioxide pressure was lower and the rate of increase of minute ventilation to carbon dioxide output was higher in the DM group. Plasma brain natriuretic peptide was higher in the DM group. delta HR/log delta NE was 19.4 +/- 4.0 in the DM group and 22.2 +/- 5.6 in the non-DM group (p < 0.01), and increased in only the non-DM group. delta HR/log delta NE was more closely correlated with peak oxygen uptake in the DM group than in the non-DM group. CONCLUSIONS: Impaired response to exercise training may be caused, in part, by impaired heart rate reserve to exercise in patients with diabetes mellitus.