[Central apneas and cardiovascular diseases]. / Apnee centrali e malattie cardiovascolari.

Central apneas (CA) and periodic breathing (PB) are the most common related breathing disorders in heart failure, being observed in up to 50% of patients. Once considered only a sleep-related phenomenon, actually CA/PB occur across the whole 24 h period and their presence in the awake patient even in the upright position and during physical effort has been associated with a worse clinical profile and a greater mortality. Chemoreflex activation, circulatory time delay and altered plant gain are the pathophysiological determinants. While the use of guideline-recommended medical and device treatment represents the first step in the management of CA in heart failure patients, no specific therapy has been demonstrated to reduce CA-related impact on mortality. In particular, the use of non-invasive ventilation has yielded contradictory results in the context of large-scale randomized clinical trials. The design and testing of therapies targeting the pathophysiological triggers of CA, such as chemoreflex sensitivity, may prove valuable in the next future.

Chemoreflex and Baroreflex Sensitivity Hold a Strong Prognostic Value in Chronic Heart Failure.

BACKGROUND: Novel treatments targeting in baroreflex sensitivity (BRS) and chemoreflex sensitivity (CRS) heart failure (HF) are grounded on small prognostic studies, partly performed in the pre-beta-blockade era. OBJECTIVES: This study assesses the clinical/prognostic significance of BRS and CRS in a large cohort of patients with chronic HF on modern treatments. METHODS: Outpatients with chronic HF with either reduced (≤40%) or mildly reduced left ventricular ejection fraction (LVEF) (41% to 49%) underwent BRS (SD method) and CRS to hypoxia and hypercapnia (rebreathing technique) assessment and were followed up for a composite endpoint of cardiac death, implantable cardioverter-defibrillator shock, or HF hospitalization. RESULTS: A total of 425 patients were enrolled (65 ± 12 years of age, LVEF 32% [IQR: 25%-38%], 94% on beta blockers). Patients with decreased BRS (n = 96 of 267, 36%) had lower exercise tolerance and heart rate variability (P < 0.05), whereas those with increased CRS to both hypoxia and hypercapnia (n = 74 of 369, 20%) had higher plasma norepinephrine and central apneas across the 24-hour period (P < 0.01). During a median 50-month follow-up (IQR: 24-94 months), the primary endpoint occurred more often in patients with decreased BRS (log-rank: 11.64; P = 0.001), mainly for increased cardiac deaths/implantable cardioverter-defibrillator shocks, and in those with increased CRS (log-rank: 34.81; P < 0.001), mainly for increased HF hospitalizations. Patients with both abnormal BRS and CRS showed the worst outcome. Reduced BRS (HR: 2.76 [95% CI: 1.36-5.63]; P = 0.005) and increased CRS (HR: 2.91 [95% CI: 1.34-6.31]; P = 0.007) were independently associated with the primary outcome and increased risk stratification when added to standard HF prognosticators (P < 0.05). CONCLUSIONS: In subjects with HF on modern treatment, abnormal BRS and CRS are frequently observed. BRS and CRS elicit autonomic imbalance, exercise limitation, unstable ventilation, and predict adverse outcomes.

Central Apneas Are More Detrimental in Female Than in Male Patients With Heart Failure.

Background Central apneas (CA) are a frequent comorbidity in patients with heart failure (HF) and are associated with worse prognosis. The clinical and prognostic relevance of CA in each sex is unknown. Methods and Results Consecutive outpatients with HF with either reduced or mildly reduced left ventricular ejection fraction (n=550, age 65±12 years, left ventricular ejection fraction 32%±9%, 21% women) underwent a 24-hour ambulatory polygraphy to evaluate CA burden and were followed up for the composite end point of cardiac death, appropriate implantable cardioverter-defibrillator shock, or first HF hospitalization. Compared with men, women were younger, had higher left ventricular ejection fraction, had lower prevalence of ischemic etiology and of atrial fibrillation, and showed lower apnea-hypopnea index (expressed as median [interquartile range]) at daytime (3 [0-9] versus 10 [3-20] events/hour) and nighttime (10 [3-21] versus 23 [11-36] events/hour) (all P<0.001), despite similar neurohormonal activation and HF therapy. Increased chemoreflex sensitivity to either hypoxia or hypercapnia (evaluated in 356 patients, 65%, by a rebreathing test) was less frequent in women (P<0.001), but chemoreflex sensitivity to hypercapnia was a predictor of apnea-hypopnea index in both sexes. At adjusted survival analysis, daytime apnea-hypopnea index ≥15 events/hour (hazard ratio [HR], 2.70; 95% CI, 1.06-7.34; P=0.037), nighttime apnea-hypopnea index ≥15 events/hour (HR, 2.84; 95% CI, 1.28-6.32; P=0.010), and nighttime CA index ≥10 events/hour (HR, 5.01; 95% CI, 1.88-13.4; P=0.001) were independent predictors of the primary end point in women but not in men (all P>0.05), also after matching women and men for possible confounders. Conclusions In chronic HF, CA are associated with a greater risk of adverse events in women than in men.

Central apnoeas and ticagrelor-related dyspnoea in patients with acute coronary syndrome.

AIMS: Dyspnoea often occurs in patients with acute coronary syndrome (ACS) treated with ticagrelor compared with other anti-platelet agents and is a cause of drug discontinuation. We aimed to explore the contribution of central apnoeas (CA) and chemoreflex sensitization to ticagrelor-related dyspnoea in patients with ACS. METHODS AND RESULTS: Sixty consecutive patients with ACS, preserved left ventricular ejection fraction, and no history of obstructive sleep apnoea, treated either with ticagrelor 90 mg b.i.d. (n = 30) or prasugrel 10 mg o.d. (n = 30) were consecutively enrolled. One week after ACS, all patients underwent two-dimensional Doppler echocardiography, pulmonary static/dynamic testing, carbon monoxide diffusion capacity assessment, 24-h cardiorespiratory monitoring for hypopnoea-apnoea detection, and evaluation of the chemosensitivity to hypercapnia by rebreathing technique. No differences were found in baseline demographic and clinical characteristics, echocardiographic, and pulmonary data between the two groups. Patients on ticagrelor, when compared with those on prasugrel, reported more frequently dyspnoea (43.3% vs. 6.7%, P = 0.001; severe dyspnoea 23.3% vs. 0%, P = 0.005), and showed higher apnoea-hypopnoea index (AHI) and central apnoea index (CAI) during the day, the night and the entire 24-h period (all P < 0.001). Similarly, they showed a higher chemosensitivity to hypercapnia (P = 0.001). Among patients treated with ticagrelor, those referring dyspnoea had the highest AHI, CAI, and chemosensitivity to hypercapnia (all P < 0.05). CONCLUSION: Central apnoeas are a likely mechanism of dyspnoea and should be screened for in patients treated with ticagrelor. A drug-related sensitization of the chemoreflex may be the cause of ventilatory instability and breathlessness in this setting.

Central and Obstructive Apneas in Heart Failure With Reduced, Mid-Range and Preserved Ejection Fraction.

Background: Although central apneas (CA) and obstructive apneas (OA) are highly prevalent in heart failure (HF), a comparison of apnea prevalence, predictors and clinical correlates in the whole HF spectrum, including HF with reduced ejection fraction (HFrEF), mid-range EF (HFmrEF) and preserved EF (HFpEF) has never been carried out so far. Materials and methods: 700 HF patients were prospectively enrolled and then divided according to left ventricular EF (408 HFrEF, 117 HFmrEF, 175 HFpEF). All patients underwent a thorough evaluation including: 2D echocardiography; 24-h Holter-ECG monitoring; cardiopulmonary exercise testing; neuro-hormonal assessment and 24-h cardiorespiratory monitoring. Results: In the whole population, prevalence of normal breathing (NB), CA and OA at daytime was 40, 51, and 9%, respectively, while at nighttime 15, 55, and 30%, respectively. When stratified according to left ventricular EF, CA prevalence decreased (daytime: 57 vs. 43 vs. 42%, p = 0.001; nighttime: 66 vs. 48 vs. 34%, p < 0.0001) from HFrEF to HFmrEF and HFpEF, while OA prevalence increased (daytime: 5 vs. 8 vs. 18%, p < 0.0001; nighttime 20 vs. 29 vs. 53%, p < 0.0001). In HFrEF, male gender and body mass index (BMI) were independent predictors of both CA and OA at nighttime, while age, New York Heart Association functional class and diastolic dysfunction of daytime CA. In HFmrEF and HFpEF male gender and systolic pulmonary artery pressure were independent predictors of CA at daytime, while hypertension predicted nighttime OA in HFpEF patients; no predictor of nighttime CA was identified. When compared to patients with NB, those with CA had higher neuro-hormonal activation in all HF subgroups. Moreover, in the HFrEF subgroup, patients with CA were older, more comorbid and with greater hemodynamic impairment while, in the HFmrEF and HFpEF subgroups, they had higher left atrial volumes and more severe diastolic dysfunction, respectively. When compared to patients with NB, those with OA were older and more comorbid independently from background EF. Conclusions: Across the whole spectrum of HF, CA prevalence increases and OA decreases as left ventricular systolic dysfunction progresses. Different predictors and specific clinical characteristics might help to identify patients at risk of developing CA or OA in different HF phenotypes.

Prognostic Significance of Central Apneas Throughout a 24-Hour Period in Patients With Heart Failure.

BACKGROUND: Large trials using noninvasive mechanical ventilation to treat central apnea (CA) occurring at night ("sleep apnea") in patients with systolic heart failure (HF) have failed to improve prognosis. The prevalence and prognostic value of CA during daytime and over an entire 24-h period are not well described. OBJECTIVES: This study evaluated the occurrence and prognostic significance of nighttime, daytime, and 24-h CA episodes in a large cohort of patients with systolic HF. METHODS: Consecutive patients receiving guideline-recommended treatment for HF (n = 525; left ventricular ejection fraction [LVEF] of 33 ± 9%; 66 ± 12 years of age; 77% males) underwent prospective evaluation, including 24-h respiratory recording, and were followed-up using cardiac mortality as an endpoint. RESULTS: The 24-h prevalence of predominant CAs (apnea/hypopnea index [AHI] ≥5 events/h, with CA of >50%) was 64.8% (nighttime: 69.1%; daytime: 57.0%), whereas the prevalence of predominant obstructive apneas (OA) was 12.8% (AHI ≥5 events/h with OAs >50%; nighttime: 14.7%; daytime: 5.9%). Episodes of CA were associated with neurohormonal activation, ventricular arrhythmic burden, and systolic/diastolic dysfunction (all p < 0.05). During a median 34-month follow-up (interquartile range [IQR]: 17 to 36 months), 50 cardiac deaths occurred. Nighttime, daytime, and 24-h moderate-to-severe CAs were associated with increased cardiac mortality (AHI of 

Prediction of the Chemoreflex Gain by Common Clinical Variables in Heart Failure.

BACKGROUND: Peripheral and central chemoreflex sensitivity, assessed by the hypoxic or hypercapnic ventilatory response (HVR and HCVR, respectively), is enhanced in heart failure (HF) patients, is involved in the pathophysiology of the disease, and is under investigation as a potential therapeutic target. Chemoreflex sensitivity assessment is however demanding and, therefore, not easily applicable in the clinical setting. We aimed at evaluating whether common clinical variables, broadly obtained by routine clinical and instrumental evaluation, could predict increased HVR and HCVR. METHODS AND RESULTS: 191 patients with systolic HF (left ventricular ejection fraction--LVEF--<50%) underwent chemoreflex assessment by rebreathing technique to assess HVR and HCVR. All patients underwent clinical and neurohormonal evaluation, comprising: echocardiogram, cardiopulmonary exercise test (CPET), daytime cardiorespiratory monitoring for breathing pattern evaluation. Regarding HVR, multivariate penalized logistic regression, Bayesian Model Averaging (BMA) logistic regression and random forest analysis identified, as predictors, the presence of periodic breathing and increased slope of the relation between ventilation and carbon dioxide production (VE/VCO2) during exercise. Again, the above-mentioned statistical tools identified as HCVR predictors plasma levels of N-terminal fragment of proBNP and VE/VCO2 slope. CONCLUSIONS: In HF patients, the simple assessment of breathing pattern, alongside with ventilatory efficiency during exercise and natriuretic peptides levels identifies a subset of patients presenting with increased chemoreflex sensitivity to either hypoxia or hypercapnia.

Influence of central apneas and chemoreflex activation on pulmonary artery pressure in chronic heart failure.

BACKGROUND: Pulmonary artery hypertension (PH), associated with increased left ventricular (LV) diastolic pressure and pulmonary vasoconstriction, is frequently observed in heart failure (HF), where it holds prognostic significance. We hypothesized that Cheyne-Stokes respiration (CSR) may contribute to increased pulmonary arterartery pressure (PAP) and right ventricular (RV) remodeling in HF, via hypoxia/hypercapnia cycles and adrenergic activation by the chemoreflex stimulation. METHODS: Seventy-two HF patients (57 males, aged 65.1 SD 12.3 years, LV ejection fraction<50%, 33.2 SD 7.5%), on guideline recommended pharmacological/device treatment underwent thorough clinical, echocardiographic and neurohormonal assessment, 24-hour cardiorespiratory screening for arrhythmias and CSR, and chemoreflex test for hypoxic (HVR) and hypercapnic (HCVR) ventilatory responses. RESULTS: Twenty patients (28%) showed significant CSR (24-hour apnea-hypopnea index, AHI≥15). Patients with CSR presented with: a) higher systolic pulmonary artery pressure (sPAP: 42.8 standard deviation-SD 10.1 vs 32.3 SD 5.7 mmHg, p<0.001), despite similar LV systolic and diastolic function; b) indexes of right chamber remodeling (all p<0.05); c) enhanced HVR (median 0.78, interquartile range-IR 0.46-1.22 vs 0.42, IR 0.18-0.67 L/min/%, p=0.01) and HCVR (1.17, IR 0.97-1.29 vs 0.72, IR 0.47-0.93 L/min/mmHg, p=0.02); d) increased plasma norepinephrine levels (690, IR 477-868 vs 366, IR 226-508 ng/L, p<0.001). Univariate predictors of sPAP>35 mmHg were AHI, HVR, HCVR; only AHI maintained its predictive value at multivariate analysis (p=0.017). CONCLUSIONS: CSR may contribute to increased pulmonary artery pressure and right chamber remodeling in HF, independently of the severity of LV systolic and diastolic dysfunction, likely via recurrent hypoxia/hypercapnia cycles and chemoreflex mediated adrenergic discharge.

Combined increased chemosensitivity to hypoxia and hypercapnia as a prognosticator in heart failure.

OBJECTIVES: The aim of the present study was to investigate the prognostic significance of chemosensitivity to hypercapnia in chronic heart failure (HF). BACKGROUND: Increased chemosensitivity to hypoxia and hypercapnia has been observed in HF. The potential value of enhanced chemosensitivity to hypercapnia to risk prediction in systolic HF has not been specifically evaluated. METHODS: One hundred ten consecutive systolic HF patients (age 62 +/- 15 years, left ventricular ejection fraction [LVEF] 31 +/- 7%) underwent assessment of chemosensitivity to hypoxia and hypercapnia (rebreathing technique) and were followed up for a median period of 29 months (range 1 to 54 months). The end point was a composite of cardiac death and aborted cardiac death (ventricular tachyarrhythmia treated by cardioverter-defibrillator). RESULTS: At baseline, 31 patients (28%) had enhanced chemosensitivity to both hypoxia and hypercapnia. Although they had the same LVEF as the 43 patients (39%) with normal chemosensitivity, they were more symptomatic (New York Heart Association functional class), had higher plasma brain natriuretic peptide and norepinephrine, steeper regression slope relating minute ventilation to carbon dioxide output (V(E)/V(CO2) slope), more Cheyne-Stokes respiration, and more ventricular arrhythmias (all p < 0.05). Four-year survival was only 49%, in marked contrast to 100% for patients with normal chemosensitivity (p < 0.001). On multivariate analysis, combined elevation in chemosensitivity was the strongest independent prognostic marker, even when adjusted for univariate predictors (V(E)/V(CO2) slope, Cheyne-Stokes respiration, LVEF, and brain natriuretic peptide, p < 0.05). CONCLUSIONS: Increased chemosensitivity to both hypoxia and hypercapnia, eliciting neurohormonal derangement, ventilation instability, and ventricular arrhythmias, is a very serious adverse prognostic marker in HF.

Risk factors and prognostic value of daytime Cheyne-Stokes respiration in chronic heart failure patients.

BACKGROUND: Sleep-related Cheyne-Stokes (CS) respiration is a known phenomenon in chronic heart failure (CHF). We aimed to study the prevalence, clinical correlates, risk factors and prognostic relevance of daytime CS, as well as its relation with neurohormonal derangement. METHODS: One hundred forty seven CHF patients with left ventricular systolic dysfunction (age: 64+/-12 years, ejection fraction, EF, 31+/-8%, mean+/-SD) underwent morning polygraphic recording, in addition to comprehensive clinical and neurohormonal evaluation. RESULTS: Daytime CS was detected in 87 patients (59%), and associated with worse NYHA class (2.6+/-0.7 vs 2.2+/-0.8, P<0.05), lower EF (29+/-8 vs 33+/-8%, P<0.05), peak oxygen consumption (11.3+/-8.3 vs 13.4+/-4 mL/min/kg, P<0.05), resting carbon dioxide level (33.1+/-4.2 vs 37.9+/-3.8 mm Hg, P<0.001), higher norepinephrine [588 (395-939) vs (331-681) ng/L, median (interquartile range) P<0.01] and natriuretic peptides [ANP: 136 (57-230) vs 66 (18-103); BNP: 284 (99-510) vs 64 (21-202); NT-proBNP: 2575 (814-3320) vs 448 (147-1599) ng/L, all: P<0.001]. At univariate analysis, CS risk factors were age, EF, carbon dioxide, creatinine, norepinephrine, natriuretic peptides, whereas age and NT-proBNP level were the only multivariate predictors. On a 33-month follow-up, CS resulted among univariate predictors of cardiac death, NT-proBNP emerging as the only variable at multivariate analysis. CONCLUSIONS: Daytime CS is frequent in CHF and is correlated with clinical severity, neurohormonal derangement, particularly of NT-proBNP, and long-term prognosis.

Clinical significance of chemosensitivity in chronic heart failure: influence on neurohormonal derangement, Cheyne-Stokes respiration and arrhythmias.

Increased chemosensitivity has been observed in HF (heart failure) and, in order to clarify its pathophysiological and clinical relevance, the aim of the present study was to investigate its impact on neurohormonal balance, breathing pattern, response to exercise and arrhythmic profile. A total of 60 patients with chronic HF [age, 66+/-1 years; LVEF (left ventricular ejection fraction), 31+/-1%; values are means+/-S.E.M.] underwent assessment of HVR (hypoxic ventilatory response) and HCVR (hypercapnic ventilatory response), neurohormonal evaluation, cardiopulmonary test, 24-h ECG monitoring, and assessment of CSR (Cheyne-Stokes respiration) by diurnal and nocturnal polygraphy. A total of 60% of patients had enhanced chemosensitivity. Those with enhanced chemosensitivity to both hypoxia and hypercapnia (i.e. HVR and HCVR), compared with those with normal chemosensitivity, had significantly (all P<0.01) higher noradrenaline (norepinephrine) and BNP (B-type natriuretic peptide) levels, higher prevalence of daytime and night-time CSR, worse NYHA (New York Heart Association) class and ventilatory efficiency [higher VE (minute ventilation)/VCO(2) (carbon dioxide output) slope], and a higher incidence of chronic atrial fibrillation and paroxysmal non-sustained ventricular tachycardia, but no difference in left ventricular volumes or LVEF. A direct correlation was found between HVR or HCVR and noradrenaline (R=0.40 and R=0.37 respectively; P<0.01), BNP (R=0.40, P<0.01), N-terminal pro-BNP (R=0.37 and R=0.41 respectively, P<0.01), apnoea/hypopnoea index (R=0.57 and R=0.59 respectively, P<0.001) and VE/VCO(2) slope (R=0.42 and R=0.50 respectively, P<0.001). Finally, by multivariate analysis, HCVR was shown to be an independent predictor of both daytime and night-time CSR. In conclusion, increased chemosensitivity to hypoxia and hypercapnia, particularly when combined, is associated with neurohormonal impairment, worse ventilatory efficiency, CSR and a higher incidence of arrhythmias, and probably plays a central pathophysiological role in patients with HF.

Neuro-hormonal activation predicts ventilatory response to exercise and functional capacity in patients with heart failure.

BACKGROUND: Heart failure (HF) is characterised by reduced tolerance to effort, associated with progressive fatigue and dyspnoea. Neuro-hormonal activation is a hallmark of HF and influences its clinical evolution. AIM: To evaluate the relationship between neuro-hormonal activation, exercise capacity and ventilatory efficiency. METHODS AND RESULTS: 154 HF patients (127 males, 62 +/- 1 years) underwent cardiopulmonary exercise testing and resting blood sampling for assay of plasma brain natriuretic peptide (BNP), NT-proBNP, norepinephrine, epinephrine, aldosterone and plasma renin activity (PRA). BNP and NT-proBNP levels correlated with peak oxygen consumption (VO2) (both R = -0.53, p < 0.001), VE/VCO2 slope (R = 0.56; p < 0.001 and R = 0.58; p < 0.001, respectively) and maximum workload (R = -0.49; p < 0.001 and R = -0.47; p < 0.001, respectively). Norepinephrine correlated slightly less with peak VO2 (R = -0.38, p < 0.001), VE/VCO2 (R = 0.45; p < 0.001) and maximum workload (R = -0.35; p < 0.001). There was a significant inverse correlation between left ventricular ejection fraction and BNP (R = -0.48, p < 0.001), NT-proBNP (R = -0.42; p < 0.001) and norepinephrine (R = -0.43; p < 0.001). Weaker correlations were found for PRA, exercise parameters and ejection fraction. ROC curves showed that BNP was able to identify patients with peak VO2 < 14 ml/min/kg (cut-off 98 pg/ml, AUC 0.775) and a VE/VCO2 > 35 (cut-off 183 pg/ml, AUC 0.797), as well as NT-proBNP (cut-off 537 pg/ml, AUC 0.799 and cut-off 1010 pg/ml, AUC 0.768, respectively) and norepinephrine (cut-off 454 pg/ml, AUC 0.716 and cut-off 575 pg/ml, AUC 0.783, respectively). CONCLUSION: Haemodynamic impairment (as indicated by BNP and NT-proBNP plasma values) and sympathetic activation predict exercise capacity and ventilatory efficiency in HF patients.