Effects of device‑guided slow breathing training on exercise capacity, cardiac function, and respiratory patterns during sleep in male and female patients with chronic heart failure

INTRODUCTION Slow breathing training (SBT) has been proposed as a new nonpharmacologic treatment in patients with chronic heart failure (CHF). OBJECTIVES The aim of this study was to assess the effects of SBT on exercise capacity, hemodynamic parameters, and sleep respiratory patterns in a relatively large sample of CHF patients. PATIENTS AND METHODS A crossover open study was conducted. Patients completed, in a random order, 10- to 12‑week SBT, with 2 15‑minute sessions of device‑guided SBT each day, reaching 6 breaths/ min, and a 10- to 12‑week follow‑up under standard care. Clinical data collection, polysomnography, echocardiography, 6‑minute walk test (6MWT), and laboratory tests were performed. RESULTS A total of 96 patients (74 men, 22 women) in New York Heart Association classes I-III, with an average age of 65 years and an ejection fraction (EF) of 31%, completed the study. Home‑based SBT was safe. After training, EF and 6MWT distance improved (EF: 31.3% ±7.3% vs 32.3% ±7.7%; P = 0.030; 6MWT: 449.9 ±122.7 m vs 468.3 ±121.9 m; P <0.001), and the apnea-hypopnea index decreased (5.6 [interquartile range (IQR), 2.1; 12.8] vs. 5.4 [IQR, 2.0; 10.8]; P = 0.043). CONCLUSIONS SBT improved physical capacity and systolic heart function; it also diminished sleep disturbances. The results support the benefits of SBT as a novel component of cardiorespiratory rehabilitation programs in patients with CHF.

Blood pressure variability: assessment, predictive value, and potential as a therapeutic target

A large body of evidence has consistently supported the relationship between blood pressure (BP) levels and the risk of cardiovascular complications. In recent years, several independent studies have also indicated that this risk may not only depend on the magnitude of the blood pressure elevation per se but also on the presence of other associated conditions such as increased blood pressure variability. This concept has been supported by a series of reports, most of which post hoc analyses of clinical trials in hypertension, showing that increasing values of BP variability (BPV) (either in the short term, in the midterm, or in the long term) may predict development, progression, and severity of cardiac, vascular, and renal organ damage, as well as cardiovascular events and mortality. Remarkably, studies conducted in populations at high cardiovascular risk have shown increasing values of BPV in the individual subjects (so-called intra- or within-individual BPV) to be strong predictors of cardiovascular morbidity and mortality, even to a larger extent than average BP values. However, in subjects at low to moderate cardiovascular risk, the contribution of BPV to cardiovascular risk prediction over and beyond average BP values has been shown to be only moderate. The aim of this paper is to critically review the evidence addressing the prognostic relevance of different components of BPV addressing a yet open question, i.e., whether routine assessment of BPV in clinical practice should be regarded as an additional target of antihypertensive treatment to improve cardiovascular protection.

Blood pressure changes in patients with chronic heart failure undergoing slow breathing training

BACKGROUND

Slow breathing training (SBT) has been proposed as a new non-pharmacological treatment able to induce favorable effects in patients with chronic heart failure (CHF). However, no information is available regarding its effects on orthostatic blood pressure (BP) changes in these patients, an issue of practical relevance given the reported BP-lowering effect of SBT. The aim of this study is to evaluate the influence of SBT on BP and whether SBT induces orthostatic hypotension (OH) or changes in quality of life (QoL) in CHF patients.

METHODS

The analysis was performed as part of an ongoing crossover open trial aimed at assessing the clinical effectiveness of SBT in treated patients with CHF. The patients underwent 10-12 weeks of SBT with the RESPeRATE device and 10-12 week follow-up under usual care. Patients were randomly divided into two groups: group I began with SBT, followed by usual care; group II began with usual care, followed by SBT. Patients undergoing SBT were asked to perform each day two separate 15 min sessions of device-guided SBT at a breathing frequency of 6 breaths/min. In all patients, before the enrollment and after each study phase, clinical data collection and BP measurements in sitting, supine and standing position were performed. OH was defined as a decrease of ≥ 20 mmHg in systolic blood pressure (SBP) or ≥ 10 mmHg in diastolic blood pressure (DBP) within 3 min of standing. QoL was assessed three times at the beginning, and after each phase of the study by the Minnesota Living with Heart Failure (MLHF) questionnaire.

RESULTS

Forty patients (two equal groups) completed the study, with the following baseline characteristics: 32 males/eight females, age 63.3 ± 13.4 years, 25 with ischemic CHF, 37 in New York Heart Association class II and three in class III, left ventricular ejection fraction 30.8 ± 6.7%, mean BP 138.7 ± 16.5/83.1 ± 11.5 mmHg, 23 with arterial hypertension and four with a history of stroke. There were no significant differences between the groups in clinical characteristics, SBP and DBP at rest, while seated and before and after standing up. OH prevalence was low and did not change during the study (10% vs 10%). No significant difference in average SBP and DBP changes secondary to body position were found when comparing the two study phases. Decrease in MLHF score was observed in group I during SBT (p = 0.002), but not in group II.

CONCLUSIONS

Our data indicate that SBT is safe, does not affect the prevalence of OH in CHF patients and shows a non-significant tendency to improve QoL. These results should be confirmed in a larger sample of patients to support the safety of SBT and its possible benefits as a novel component of cardiorespiratory rehabilitation programs in CHF.

Ethnic Differences in the Degree of Morning Blood Pressure Surge and in Its Determinants Between Japanese and European Hypertensive Subjects

Morning blood pressure (BP) surge has been reported to be a prognostic factor for cardiovascular events. Its determinants are still poorly defined, however. In particular, it is not clear whether ethnic differences play a role in determining morning surge (MS) size. Aim of our study was to explore whether differences exist in the size of MS between Japanese and Western European hypertensive patients. We included 2887 untreated hypertensive patients (age 62.3±8.8 years) from a European ambulatory BP monitoring database and 811 hypertensive patients from a Japanese database (Jichi Medical School Ambulatory Blood Pressure Monitoring WAVE1, age 72.3±9.8 years) following the same inclusion criteria. Their 24-hour ambulatory BP monitoring recordings were analyzed focusing on MS. Sleep-trough MS was defined as the difference between mean systolic BP during the 2 hours after awakening and mean systolic BP during the 1-hour night period that included the lowest sleep BP level. The sleep-trough MS was higher in Japanese than in European hypertensive patients after adjusting for age and 24-hour mean BP levels (40.1 [95% confidence interval 39.0–41.2] versus 23.0 [22.4–23.5] mm Hg; P <0.001). This difference remained significant after accounting for differences in night-time BP dipping. Age was independently associated with MS in the Japanese database, but not in the European subjects. Our results for the first time show the occurrence of substantial ethnic differences in the degree of MS. These findings may help in understanding the role of ethnic factors in cardiovascular risk assessment and in identifying possible ethnicity-related differences in the most effective measures to be implemented for prevention of BP-related cardiovascular events.

Effects of hypobaric hypoxia exposure at high altitude on left ventricular twist in healthy subjects: data from HIGHCARE study on Mount Everest

AIMS

Previous studies investigating the effect of hypoxia on left ventricle focused on its global function, an approach that may not detect a selective dysfunction of subendocardial layers that are most sensitive to an inadequate oxygen supply. In the HIGHCARE study, aimed at exploring the effects of high altitude hypoxia on multiple biological variables and their modulation by an angiotensin receptor blocker, we addressed the effects of hypobaric hypoxia on both systolic and diastolic left ventricular geometry and function, focusing on echocardiographic assessment of left ventricle twist to indirectly examine subendocardial left ventricular systolic function.

METHODS AND RESULTS

In 39 healthy subjects, physiological and echocardiographic variables, including left ventricular twist and a simplified torsion-to-shortening ratio (sTSR), were recorded at sea level, at 3400 m, and at 5400 m altitude (Mount Everest base camp). Both left ventricular twist and sTSR were greater at 5400 m than at sea level (12.6° vs. 9.6° and 0.285 vs. 0.202, P < 0.05 for both), were linearly related to the reduction in arterial oxygen partial pressure (P < 0.01 for both), and were associated with significant changes in LV dimensions and contractility. No effects of angiotensin receptor blockade were observed on these variables throughout the study.

CONCLUSION

Our study, for the first time, demonstrates an increase in left ventricular twist at high altitude in healthy subjects exposed to high altitude hypoxia, suggesting the occurrence of subendocardial systolic dysfunction in such condition.

Sex and acetazolamide effects on chemoreflex and periodic breathing during sleep at altitude

OBJECTIVE

Nocturnal periodic breathing occurs more frequently in men than in women with various clinical and pathophysiologic conditions. The mechanisms accounting for this sex-related difference are not completely understood. Acetazolamide effectively counteracts nocturnal periodic breathing, but it has been investigated almost exclusively in men. Our aim was to explore possible determinants of nocturnal periodic breathing in a high-altitude setting both in men and in women. We hypothesized that increased hypoxic chemosensitivity in men could be associated with the development of nocturnal periodic breathing at altitude more frequently than in women, and that acetazolamide, by leftward shifting the CO2 ventilatory response, could improve nocturnal periodic breathing at altitude in a sex-independent manner.

METHODS

Forty-four healthy lowlanders (21 women), randomized to acetazolamide or placebo, underwent cardiorespiratory sleep studies at sea level off treatment and under treatment on the first night after arrival at a 4,559-m altitude. Hypoxic and hypercapnic chemosensitivities were assessed at sea level.

RESULTS

Men, more frequently than women, exhibited increased hypoxic chemosensitivity and displayed nocturnal periodic breathing at altitude. Acetazolamide leftward shifted the CO2 set point and, at altitude, improved oxygenation and reduced periodic breathing in both sexes, but to a larger extent in men. Hypoxic chemosensitivity directly correlated with the number of apneas/hypopneas at altitude in the placebo group but not in the acetazolamide group.

CONCLUSIONS

The greater severity of periodic breathing during sleep displayed by men at altitude could be attributed to their increased hypoxic chemosensitivity. Acetazolamide counteracted the occurrence of periodic breathing at altitude in both sexes, modifying the apneic threshold and improving oxygenation.

TRIAL REGISTRY

EU Clinical Trials Register, EudraCT; No.: 2010-019986-27; URL: https://www.clinicaltrialsregister.eu.

Diastolic dysfunction in controlled hypertensive patients with mild-moderate obstructive sleep apnea

BACKGROUND

Hypertension and severe obstructive sleep apnea (OSA) may independently contribute to left ventricular diastolic dysfunction. However, scanty data is available on this issue in hypertensives with mild-moderate OSA.

METHODS AND RESULTS

We performed polysomnography, echocardiography and 24h ambulatory blood pressure monitoring in 115 treated essential hypertensives with suspicion of OSA. After exclusion of severe/treated OSA and/or cardiovascular disease patients, mild-moderate OSA (5 ≤ apnoea/hypopnoea index<30 events·h(-1)) was diagnosed in 47.3% of the remaining 91 patients, while 52.7% were free of OSA. Transmitral early (E) and late (A) peak flow velocities were assessed in 69 patients, and mitral annular velocity (E') in 53. Compared to non-OSA, mild-moderate OSA heart rate was higher (p=0.031) while E/A was lower (p<0.001) without differences in 24h mean systolic and diastolic blood pressures (125.36 ± 12.46/76.46 ± 6.97 vs 128.63 ± 11.50/77.70 ± 7.72 mmHg, respectively, NS). Patients with E'< 10 cm/s and E/A<0.8 showed a lower mean SpO2 than subjects with normal diastolic function (p=0.004; p<0.001). In a logistic regression model age, mean SpO2, daytime heart rate and nocturnal diastolic blood pressure fall were associated with altered relaxation pattern, independently from BMI and gender.

CONCLUSIONS

In controlled hypertensives mild-moderate OSA may be associated with early diastolic dysfunction, independently from age, gender and mean blood pressure and in the absence of concentric left ventricular hypertrophy. Moreover nocturnal hypoxia may be a key factor in determining early diastolic dysfunction, under the synergic effects of hypertension and mild-moderate OSA.

Insulin resistance and beat-to-beat cardiovascular dynamics: a constant relationship across different body mass index and blood pressure categories

CONTEXT

Epidemiological studies have shown a progressive increase in insulin resistance (IR) accompanying body weight gain and blood pressure (BP) increase. This has led to the consideration that hemodynamic effects of IR might depend on its relationship with body mass index (BMI) and BP.

OBJECTIVE

The aim of our study was to determine whether IR is associated with changes in hemodynamic indices of cardiovascular function across different categories of BMI (normal weight, overweight, and obese), and BP levels (normal, high normal, and hypertension).

DESIGN, SETTING AND PARTICIPANTS

This was a cross-sectional study conducted in a population sample of nondiabetic individuals (n = 731).

MEASURES

Insulin resistance was evaluated with the homeostasis model assessment of insulin resistance (HOMA) and subjects were classified into quartiles according to HOMA index values. Synchronized beat-to-beat recordings of stroke volume (impedance cardiography) and R-R interval, along with repeated auscultatory BP measurements were performed. Derived hemodynamic parameters were computed and averaged.

RESULTS

Analysis of covariance adjusting for confounders showed significant differences for most hemodynamic parameters among different quartiles of HOMA index both in the general population and within each BMI and BP category. Overall, increasing values of HOMA index were associated with significantly higher BP; and reduced R-R interval, stroke index, cardiac index, pre-ejection period and left ventricular ejection time (P < .01) across different categories of BMI and BP.

CONCLUSIONS

These findings suggest that even small increases in HOMA index (not necessarily in the range to define IR) may induce significant changes on indices of cardiovascular function even in normal-weight and normotensive subjects, emphasizing the importance of IR at an early stage of the cardiovascular risk continuum.