Coronary flow reserve is impaired in patients with obstructive sleep apnea

Differences in coronary microcirculation measurements during regadenoson vs. adenosine - induced hyperemia

BACKGROUND

Little is known about the similarity of microcirculation assessment outcomes performed with regadenoson and adenosine. The aim of the current study was to compare coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) assessment using adenosine and regadenoson, and to evaluate predictors regarding the size of differences.

METHODS

44 patients were enrolled and diagnosed between 2021 and 2023. Fractional flow reserve (FFR), CFR and IMR were measured twice in the circumflex (Cx) (n = 8) or left anterior descending (LAD) (n = 36) artery: once with continuous infusion of adenosine (Adenocor 140 µg/kg/min) and 10 minutes later with regadenoson (Rapiscan 400 µg i.v.).

RESULTS

Averaged results were quantified with adenosine and regadenoson for FFR (0.81 [0.75 ÷ 0.89] vs. 0.80 [0.73 ÷ 0.88]), CFR (3.84 [1.67 ÷ 4.08] vs. 3.97 [1.78 ÷ 4.32]) and IMR (20.01 [11 ÷ 24.5] vs. 20.25 [10.75 ÷ 23]), respectively. None of the differences were statistically significant. Among the significant (p < 0.05) predictors of greater ΔCFR, the following can be noted: prior percutaneous transluminal angioplasty/carotid artery stenting (β = 2.35), oral anticoagulant usage (β = 0.89), and prior stroke/transient ischaemic attack (TIA) (β = 1.09), with the latter being also confirmed for greater ΔIMR (β = 8.89). Moreover, patients with New York Heart Association (NYHA) class II/III, as compared to those with NYHA class I, were more likely to have greater ΔIMR (β = 11.89).

CONCLUSIONS

Regadenoson may be a feasible alternative to adenosine in coronary microcirculation assessment, as it produces similar outcomes. Selected factors were found to be predictors of greater differences in IMR, CFR and FFR values according to the agent used for coronary hyperemia.

Mineralocorticoid receptor antagonism prevents coronary microvascular dysfunction in intermittent hypoxia independent of blood pressure

STUDY OBJECTIVES

Obstructive sleep apnea (OSA), characterized by intermittent hypoxia (IH), and is associated with increased cardiovascular mortality that may not be reduced by standard therapies. Inappropriate activation of the renin-angiotensin-aldosterone system occurs in IH, and mineralocorticoid receptor (MR) blockade has been shown to improve vascular outcomes in cardiovascular disease. Thus, we hypothesized that MR inhibition prevents coronary and renal vascular dysfunction in mice exposed to chronic IH.

METHODS

Human and mouse coronary vascular cells and male C57BL/6J mice were exposed to IH or room air (RA) for 12 hours/day for 3 days (in vitro) and 6 weeks with or without treatments with spironolactone (SPL) or hydrochlorothiazide (HTZ).

RESULTS

In vitro studies demonstrated that IH increased MR gene expression in human and mouse coronary artery endothelial and smooth muscle cells. Exposure to IH in mice increased blood pressure, reduced coronary flow velocity reserve (CFVR), and attenuated endothelium-dependent dilation and enhanced vasoconstrictor responsiveness in coronary, but not renal arteries. Importantly, SPL treatment prevented altered coronary vascular function independent of blood pressure as normalization of BP with HTZ did not improve CFVR or coronary vasomotor function.

CONCLUSIONS

These data demonstrate that chronic IH, which mimics the hypoxia-reoxygenation cycles of moderate-to-severe OSA, increases coronary vascular MR expression in vitro. It also selectively promotes coronary vascular dysfunction in mice. Importantly, this dysfunction is sensitive to MR antagonism by SPL, independent of blood pressure. These findings suggest that MR blockade could serve as an adjuvant therapy to improve long-term cardiovascular outcomes in patients with OSA.

Implementation of Microcirculation Examination in Clinical Practice-Insights from the Nationwide POL-MKW Registry

Background and Objectives: The assessment of coronary microcirculation may facilitate risk stratification and treatment adjustment. The aim of this study was to evaluate patients' clinical presentation and treatment following coronary microcirculation assessment, as well as factors associated with an abnormal coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) values. Materials and Results: This retrospective analysis included 223 patients gathered from the national registry of invasive coronary microvascular testing collected between 2018 and 2023. Results: The frequency of coronary microcirculatory assessments in Poland has steadily increased since 2018. Patients with impaired IMR (≥25) were less burdened with comorbidities. Patients with normal IMR underwent revascularisation attempts more frequently (11.9% vs. 29.8%, p = 0.003). After microcirculation testing, calcium channel blockers (CCBs) and angiotensin-converting enzyme inhibitors were added more often for patients with IMR and CFR abnormalities, respectively, as compared to control groups. Moreover, patients with coronary microvascular dysfunction (CMD, defined as CFR and/or IMR abnormality), regardless of treatment choice following microcirculation assessment, were provided with trimetazidine (23.2%) and dihydropyridine CCBs (26.4%) more frequently than those without CMD who were treated conservatively (6.8%) and by revascularisation (4.2% with p = 0.002 and 0% with p < 0.001, respectively). Multivariable analysis revealed no association between angina symptoms and IMR or CFR impairment. Conclusions: The frequency of coronary microcirculatory assessments in Poland has steadily increased. Angina symptoms were not associated with either IMR or CFR impairment. After microcirculation assessment, patients with impaired microcirculation, expressed as either low CFR, high IMR or both, received additional pharmacotherapy treatment more often.

Coronary Microvascular Dysfunction and Hypertension: A Bond More Important than We Think

Coronary microvascular dysfunction (CMD) is a clinical entity linked with various risk factors that significantly affect cardiac morbidity and mortality. Hypertension, one of the most important, causes both functional and structural alterations in the microvasculature, promoting the occurrence and progression of microvascular angina. Endothelial dysfunction and capillary rarefaction play the most significant role in the development of CMD among patients with hypertension. CMD is also related to several hypertension-induced morphological and functional changes in the myocardium in the subclinical and early clinical stages, including left ventricular hypertrophy, interstitial myocardial fibrosis, and diastolic dysfunction. This indicates the fact that CMD, especially if associated with hypertension, is a subclinical marker of end-organ damage and heart failure, particularly that with preserved ejection fraction. This is why it is important to search for microvascular angina in every patient with hypertension and chest pain not associated with obstructive coronary artery disease. Several highly sensitive and specific non-invasive and invasive diagnostic modalities have been developed to evaluate the presence and severity of CMD and also to investigate and guide the treatment of additional complications that can affect further prognosis. This comprehensive review provides insight into the main pathophysiological mechanisms of CMD in hypertensive patients, offering an integrated diagnostic approach as well as an overview of currently available therapeutical modalities.

Temporal changes in coronary artery function and flow velocity reserve in mice exposed to chronic intermittent hypoxia

Study Objectives

Obstructive sleep apnea (OSA) is a chronic condition characterized by intermittent hypoxia (IH) that is implicated in an increased risk of cardiovascular disease (i.e., coronary heart disease, CHD) and associated with increased overall and cardiac-specific mortality. Accordingly, we tested the hypothesis that experimental IH progressively impairs coronary vascular function and in vivo coronary flow reserve.

Methods

Male C57BL/6J mice (8-week-old) were exposed to IH (FiO2 21% 90 s–6% 90 s) or room air (RA; 21%) 12 h/day during the light cycle for 2, 6, 16, and 28 weeks. Coronary artery flow velocity reserve (CFVR) was measured at each time point using a Doppler system. After euthanasia, coronary arteries were micro-dissected and mounted on wire myograph to assess reactivity to acetylcholine (ACh) and sodium nitroprusside (SNP).

Results

Endothelium-dependent coronary relaxation to ACh was preserved after 2 weeks of IH (80.6 ± 7.8%) compared to RA (87.8 ± 7.8%, p = 0.23), but was significantly impaired after 6 weeks of IH (58.7 ± 16.2%, p = 0.02). Compared to ACh responses at 6 weeks, endothelial dysfunction was more pronounced in mice exposed to 16 weeks (48.2 ± 5.3%) but did not worsen following 28 weeks of IH (44.8 ± 11.6%). A 2-week normoxic recovery after a 6-week IH exposure reversed the ACh abnormalities. CFVR was significantly reduced after 6 (p = 0.0006) and 28 weeks (p &lt; 0.0001) of IH when compared to controls.

Conclusion

Chronic IH emulating the hypoxia-re-oxygenation cycles of moderate-to-severe OSA promotes coronary artery endothelial dysfunction and CFVR reductions in mice, which progressively worsen until reaching asymptote between 16 and 28 weeks. Normoxic recovery after 6 weeks exposure reverses the vascular abnormalities.

Cardiac function and cognitive function in patients with obstructive sleep apnea

Objectives

This study was designed to evaluate echocardiographic findings in patients with obstructive sleep apnea (OSA) with cognitive impairment and compare it with the control group.

Methods

Sixty-seven OSA patients and 52 group of healthy controls were evaluated prospectively by Mini-Mental State Examination questionnaire and trans-thoracic echocardiography.

Results

The cognitive impairment and diastolic dysfunction were 19.6% (P = .002) and 18.4% (P = .016) more prevalent in OSA group compared to the control group. The mean tricuspid regurgitant gradient, pulmonary artery size, and transmitral A velocity were higher, but mean right ventricular peak systolic velocity, tricuspid annular plane systolic excursion (TAPSE), fractional area change (FAC), transmitral E/A ratio, and annular E’ velocity were lower in the OSA group than the control group. Comparing the patients with and without cognitive disorders, showed significant differences regarding the size of right atrium, TAPSE and FAC (P < .05).

Conclusions

OSA patients need accurate cardiac examinations, early diagnosis, and interventions to prevent the progression of cardiac dysfunction, especially older male patients with higher BMI and impaired cognition. Further studies are needed to determine the exact link between the OSA, obesity, and cardiac physiology.

Obstructive sleep apnea is associated with coronary microvascular dysfunction: A systematic review from a clinical perspective

There is now increasing evidence demonstrating that obstructive sleep apnea (OSA) contributes to microvascular disorder. However, whether OSA is associated with impaired coronary flow reserve is still unclear. Therefore, we conducted this systematic review and meta‐analysis to summarize current evidence. In a systematic review, PubMed, Embase, the Cochrane Library and Web of Science were searched; five observational studies fulfilled the selection criteria and were included in this study. Data were extracted from selected studies and meta‐analysis was performed using random‐effects modelling. In all, 829 OSA patients and 507 non‐OSA subjects were included and assessed for coronary flow reserve (CFR), the clinical indicator of coronary microvascular dysfunction (CMD). For all studies, OSA was significantly associated with reduced CFR. The pooled weighted mean difference (WMD) of CFR was −0.78 (95% confidence interval [CI] −1.25 to −0.32, p ＜ 0.001, I² = 84.4%). The difference in the apnea–hypopnea index (AHI) between studies can explain 89% of heterogeneity (coef = −0.05, 95% CI −0.12 to 0.02, p = .078) in a meta‐regression, indicating the CFR tended to negatively correlate with severity of OSA. The Egger regression test did not show statistical significance (p = .49). In conclusion, there are plausible biological mechanisms linking OSA and CMD, and the preponderance of evidence from this systematic review suggests that OSA, especially severe OSA, is associated with reduced CFR. Future studies are warranted to further delineate the exact role of OSA in CMD occurrence and development in a prospective setting.