Acute effect of esmolol intravenously on coronary microcirculation in patients with idiopathic dilated cardiomyopathy

Chinese expert consensus on the diagnosis and treatment of coronary microvascular diseases (2023 Edition)

Since the four working groups of the Chinese Society of Cardiology issued first expert consensus on coronary microvascular diseases (CMVD) in 2017, international consensus documents on CMVD have increased rapidly. Although some of these documents made preliminary recommendations for the diagnosis and treatment of CMVD, they did not provide classification of recommendations and levels of evidence. In order to summarize recent progress in the field of CMVD, standardize the methods and procedures of diagnosis and treatment, and identify the scientific questions for future research, the four working groups of the Chinese Society of Cardiology updated the 2017 version of the Chinese expert consensus on CMVD and adopted a series of measures to ensure the quality of this document. The current consensus has raised a new classification of CMVD, summarized new epidemiological findings for different types of CMVD, analyzed key pathological and molecular mechanisms, evaluated classical and novel diagnostic technologies, recommended diagnostic pathways and criteria, and therapeutic strategies and medications, for patients with CMVD. In view of the current progress and knowledge gaps of CMVD, future directions were proposed. It is hoped that this expert consensus will further expedite the research progress of CMVD in both basic and clinical scenarios.

Beta-1 vs. beta-2 adrenergic control of coronary blood flow during isometric handgrip exercise in humans

During exercise, β-adrenergic receptors are activated throughout the body. In healthy humans, the net effect of β-adrenergic stimulation is an increase in coronary blood flow. However, the role of vascular β1 vs. β2 receptors in coronary exercise hyperemia is not clear. In this study, we simultaneously measured noninvasive indexes of myocardial oxygen supply (i.e., blood velocity in the left anterior descending coronary artery; Doppler echocardiography) and demand [i.e., rate pressure product (RPP) = heart rate × systolic blood pressure) and tested the hypothesis that β1 blockade with esmolol improves coronary exercise hyperemia compared with nonselective β-blockade with propranolol. Eight healthy young men received intravenous infusions of esmolol, propranolol, and saline on three separate days in a single-blind, randomized, crossover design. During each infusion, subjects performed isometric handgrip exercise until fatigue. Blood pressure, heart rate, and coronary blood velocity (CBV) were measured continuously, and RPP was calculated. Changes in parameters from baseline were compared with paired t-tests. Esmolol (Δ = 3296 ± 1204) and propranolol (Δ = 2997 ± 699) caused similar reductions in peak RPP compared with saline (Δ = 5384 ± 1865). In support of our hypothesis, ΔCBV with esmolol was significantly greater than with propranolol (7.3 ± 2.4 vs. 4.5 ± 1.6 cm/s; P = 0.002). This effect was also evident when normalizing ΔCBV to ΔRPP. In summary, not only does selective β1 blockade reduce myocardial oxygen demand during exercise, but it also unveils β2-receptor-mediated coronary exercise hyperemia.NEW & NOTEWORTHY In this study, we evaluated the role of vascular β1 vs. β2 receptors in coronary exercise hyperemia in a single-blind, randomized, crossover study in healthy men. In response to isometric handgrip exercise, blood flow velocity in the left anterior descending coronary artery was significantly greater with esmolol compared with propranolol. These findings increase our understanding of the individual and combined roles of coronary β1 and β2 adrenergic receptors in humans.

Esmolol infusion versus propranolol infusion: effects on heart rate and blood pressure in healthy volunteers

Despite its widespread clinical use, the β1-adrenergic receptor antagonist esmolol hydrochloride is not commonly used in human physiology research, and the effective dose of esmolol (compared with the nonselective β-blocker propranolol) is unclear. In four separate studies we used cycle ergometry exercise and infusions of isoproterenol and epinephrine to test the heart rate (HR)-lowering effect of esmolol compared with propranolol and saline in healthy humans. In cohort 1, both esmolol (ΔHR 57 ± 6 beats/min) and propranolol (ΔHR 56 ± 7 beats/min) attenuated exercise tachycardia compared with saline (ΔHR 88 ± 17 beats/min). In cohort 2, we found that the HR response to exercise was similar at 5 min (ΔHR 57 ± 9 beats/min) and 60 min (ΔHR 55 ± 9 beats/min) after initiation of the esmolol maintenance infusion. In cohort 3, we confirmed that the HR-lowering effect of esmolol disappeared 45 min after termination of the maintenance infusion. In cohort 4, changes in femoral blood flow and hematological parameters in response to epinephrine infusion were not different between esmolol and saline infusion, indicating that our esmolol infusion paradigm does not block β2-receptors. Collectively, our data indicate that infusion of ~160 mg of esmolol (range 110-200 mg in the 5 min before exercise) acutely and selectively blocks β1-receptors in healthy humans. Additionally, β1-receptors remain blocked 60 min later if a maintenance infusion of ~0.2 mg·kg total body mass-1·min-1 continues. The current data lay the foundation for future studies to evaluate β1- vs. β2-receptor control of the circulation in humans.NEW & NOTEWORTHY We used cycle ergometry exercise and infusions of isoproterenol and epinephrine to test the heart rate-lowering effect of esmolol compared with propranolol and saline in healthy humans. Collectively, our data indicate that infusion of ~160 mg of esmolol (range 110-200 mg in the 5 min before exercise) acutely and selectively blocks β1-adrenergic receptors. These infusion parameters can be used in future experiments to evaluate β1- vs. β2-receptor control of the circulation in humans.

Gut and sublingual microvascular effect of esmolol during septic shock in a porcine model

INTRODUCTION

Esmolol may efficiently reduce heart rate (HR) and decrease mortality during septic shock. An improvement of microcirculation dissociated from its macrocirculatory effect may a role. The present study investigated the effect of esmolol on gut and sublingual microcirculation in a resuscitated piglet model of septic shock.

METHODS

Fourteen piglets, anesthetized and mechanically ventilated, received a suspension of live Pseudomonas aeruginosa. They were randomly assigned to two groups: the esmolol (E) group received an infusion of esmolol, started at 7.5 μg⋅kg(-1)⋅min(-1), and progressively increased to achieve a HR below 90 beats⋅min(-1). The control (C) group received an infusion of Ringer's lactate solution. HR, mean arterial pressure (MAP), cardiac index (CI), stroke index (SI), systemic vascular resistance (SVR), arterio-venous blood gas and lactate were recorded. Oxygen consumption (VO2), delivery (DO2) and peripheral extraction (O2ER) were computed. Following an ileostomy, a laser Doppler probe was applied on ileal mucosa to monitor gut microcirculatory laser Doppler flow (GMLDF). Videomicroscopy was also used on ileal mucosa and sublingual areas to evaluate mean flow index (MFI), heterogeneity, ratio of perfused villi and proportion of perfused vessels. Resuscitation maneuvers were performed following a defined algorithm.

RESULTS

Bacterial infusion induced a significant alteration of the gut microcirculation with an increase in HR. Esmolol produced a significant time/group effect with a decrease in HR (P <0.004) and an increase in SVR (P <0.004). Time/group effect was not significant for CI and MAP, but there was a clear trend toward a decrease in CI and MAP in the E group. Time/group effect was not significant for SI, O2ER, DO2, VO2, GMLDF and lactate. A significant time/group effect of ileal microcirculation was found with a lower ileal villi perfusion (P <0.025) in the C group, and a trend toward a better MFI in the E group. No difference between both groups was found regarding microcirculatory parameters in the sublingual area.

CONCLUSIONS

Esmolol provided a maintenance of microcirculation during sepsis despite its negative effects on macrocirculation. Some parameters even showed a trend toward an improvement of the microcirculation in the gut area in the esmolol group.

Ivabradine improves coronary flow reserve in patients with stable coronary artery disease

OBJECTIVES

Although treatment with ivabradine reduces the incidence of hospital admissions for myocardial infarction and coronary revascularisation, there are no data concerning its effect on coronary circulation. The purpose of this study was to assess the effects of ivabradine on coronary flow velocity and flow reserve (CFR) in patients with stable coronary artery disease (CAD).

METHODS

During diagnostic coronary angiography (baseline), twenty-one patients with stable CAD underwent coronary flow velocity measurements (APV cm/s) in a non-culprit vessel, using a Doppler guidewire, at rest (r) and after adenosine administration to achieve maximal hyperaemia (h). During programmed coronary intervention in the culprit vessel, the same measurements were repeated one week after treatment with ivabradine (5 mg twice daily), both at the intrinsic heart rate and at a paced heart rate identical to that before treatment. CFR was defined as h-APV/r-APV.

RESULTS

Heart rate was significantly lower after treatment with ivabradine (78±14 bpm vs 65±9 bpm, p<0.001). Also, a reduction of r-APV (17.0±5.5 vs 19.7±7.6, p=0.003) and augmentation of h-APV (57.9±17.8 vs 53.5±21.4, p=0.009) leading to CFR improvement (3.51±0.81 vs 2.78±0.61, p<0.001) were observed. During pacing, although r-APV reverted to values similar to those before treatment (20.0±6.5 vs 19.7±7.6, p=NS), a sustained improvement in h-APV was observed (59.5±19.7 vs 53.5±21.4, p=0.007) and CFR remained higher than before treatment (3.04±0.66 vs 2.78±0.61, p<0.001).

CONCLUSIONS

Ivabradine treatment significantly improves hyperaemic coronary flow velocity and CFR in patients with stable CAD. These effects remain even after heart rate correction indicating improved microvascular function.