Influence of myocardial oxygen demand on the coronary vascular response to arterial blood gas changes in humans

When two Z-scores meet-analysis of exercise capacity of children and adolescents with Kawasaki disease by a new Z-score model of coronary artery and a new Z-score evaluating peak oxygen consumption : Coronary artery Z-score and peakVO2 Z-score in KD

BACKGROUND

Coronary artery (CA) Z-score system is widely used to define CA aneurysm (CAA). Children and adolescents after acute stage of Kawasaki disease (KD-CA) have a higher risk of developing CAAs if their CA Z-score ≥ 2.5. Z-score system of peak oxygen consumption (Peak VO2 Z-score) allows comparisons across ages and sex, regardless of body size and puberty. We aimed to compare the exercise capacity (EC) indicated by peak VO2 Z-score during cardiopulmonary exercise testing (CPET) directly between KD-CA with different CA Z-score.

METHODS

KD-CA after acute stage who received CPET in the last 5 years were retrospectively recruited. CA Z-score was based on Lambda-Mu-Sigma method. Max-Z was the maximum CA Z-score of different CAs. KD children with Max-Z < 2.5 and ≥ 2.5 were defined as KD-1 and KD-2 groups, respectively. Peak VO2 Z-score was calculated using the equation established based on Hong Kong Chinese children and adolescent database.

RESULTS

One hundred two KD-CA were recruited (mean age: 11.71 ± 2.57 years). The mean percent of measured peak VO2 to predicted value (peak PD%) was 90.11 ± 13.33. All basic characteristics and baseline pulmonary function indices were comparable between KD-1 (n = 87) and KD-2 (n = 15). KD-1 had significantly higher peak VO2 Z-score (p = .025), peak PD% (p = .008), peak metabolic equivalent (p = .027), and peak rate pressure product (p = .036) than KD-2.

CONCLUSIONS

KD-CA had slightly reduced EC than healthy peers. KD-CA with Max-Z ≥ 2.5 had significantly lower peak EC than those < 2.5. Max-Z is potentially useful follow-up indicator after acute stage of KD.

The coronary vascular response to the metaboreflex at low-altitude and during acute and prolonged high-altitude in males

Myocardial oxygen delivery is primarily regulated through changes in vascular tone to match increased metabolic demands. In males, activation of the muscle metaboreflex during acute isocapnic hypoxia results in a paradoxical coronary vasoconstriction. Whether coronary blood velocity is reduced by metaboreflex activation following travel and/or adaptation to high-altitude is unknown. This study determined if the response of the coronary vasculature to muscle metaboreflex activation at low-altitude differs from acute (1/2 days) and prolonged (8/9 days) high-altitude. Healthy males (n=16) were recruited and performed isometric handgrip exercise (30 % max) followed by post-exercise circulatory occlusion (PECO) to isolate the muscle metaboreflex at low-altitude and following acute and prolonged high-altitude (3,800 m). Mean left anterior descending coronary artery blood velocity (LADv_mean, transthoracic Doppler echocardiography), heart rate, mean arterial pressure (MAP), ventilation, and respired gases were assessed during baseline and PECO at all time-points. Coronary vascular conductance index (CVC_i) was calculated as LAD_Vmean/MAP. The change in LADv_mean (acute altitude: -1.7 ± 3.9 cm/s, low-altitude: 2.6 ± 3.4 cm/s, P = 0.01) and CVC_i (acute altitude: -0.05 ± 0.04 cm/s/mmHg, low-altitude: -0.01 ± 0.03 cm/s/mmHg, P = 0.005) induced by PECO differed significantly between acute high-altitude and low-altitude. The change in LAD_Vmean and CVC_i induced by PECO following prolonged high-altitude was not different from low-altitude. Our results suggest that coronary vasoconstriction with metaboreflex activation in males is greatest following acute ascent to high-altitude and restored to low-altitude levels following 8-9 days of acclimatization.

Serial Exercise Testing and Echocardiography Findings of Patients With Kawasaki Disease

OBJECTIVE

Kawasaki disease (KD) is the most common form of pediatric vasculitis. We evaluated the influence of KD on cardiopulmonary function and analyzed the echocardiographic findings of patients with KD through serial follow-ups from childhood to adolescence.

METHODS

This was a retrospective study. We recruited patients with KD after the acute stage who underwent at least two (with >1-year interval between visits) cardiopulmonary exercise testing (CPET) and echocardiographic examinations in the last 10 years. Cardiopulmonary function was determined through CPET on a treadmill. The maximum Z score (Max-Z) of the proximal left anterior descending coronary artery or right coronary artery was determined using echocardiography. Healthy peers matched for age, sex, and body mass index with serial CPET and echocardiographic data were recruited as a control group.

RESULTS

Each group consisted of 30 participants with comparable basic characteristics. No significant differences in the variables of the first CPET were observed between the two groups. In the final CPET, the control group had a higher percentage of measured oxygen consumption (Vo₂) at the anaerobic threshold (AT) to the predicted peak Vo₂ (p = 0.016), higher percentage of measured peak Vo₂ to the predicted peak Vo₂ (p = 0.0004), and higher Vo₂ at AT (p < 0.0001) than those of the KD group. No significant difference in the percentage of distribution of Max-Z was observed between the first and final echocardiographic examinations.

CONCLUSIONS

Children with a history of KD had comparable exercise capacity to their healthy peers. However, in the follow-up, the aerobic metabolism and peak exercise load capacities of adolescents with KD were significantly lower than those of control adolescents.

Sex differences in the coronary vascular response to combined chemoreflex and metaboreflex stimulation in healthy humans

NEW FINDINGS

What is the central question of this study? Coronary blood flow in healthy humans is controlled by both local metabolic signalling and adrenergic activity: does the integration of these signals during acute hypoxia and adrenergic activation differ between sexes? What are the main findings and its importance? Both males and females exhibit an increase in coronary blood velocity in response to acute hypoxia, a response that is constrained by adrenergic stimulation in males but not females. These findings suggest that coronary blood flow control differs between males and females.

ABSTRACT

Coronary hyperaemia is mediated through multiple signalling pathways, including local metabolic messengers and adrenergic stimulation. This study aimed to determine whether the coronary vascular response to adrenergic stressors is different between sexes in normoxia and hypoxia. Young, healthy participants (n = 32; 16F) underwent three randomized trials of isometric handgrip exercise followed by post-exercise circulatory occlusion (PECO) to activate the muscle metaboreflex. End-tidal P O 2 was controlled at (1) normoxic levels throughout the trial, (2) 50 mmHg for the duration of the trial (hypoxia trial), or (3) 50 mmHg only during PECO (mixed trial). Mean left anterior descending coronary artery velocity (LAD_Vmean ; transthoracic Doppler echocardiography), heart rate and blood pressure were assessed at baseline and during PECO. In normoxia, there was no change in LAD_Vmean or cardiac workload induced by PECO in males and females. Acute hypoxia increased baseline LAD_Vmean to a greater extent in males compared with females (P < 0.05), despite a similar increase in cardiac workload. The change in LAD_Vmean induced by PECO was similar between sexes in normoxia (P = 0.31), greater in males during the mixed trial (male: 12.8 (7.7) cm/s vs. female: 8.1 (6.3) cm/s; P = 0.02) and reduced in males but not females in acute hypoxia (male: -4.8 (4.5) cm/s vs. female: 0.8 (6.2) cm/s; P = 0.006). In summary, sex differences in the coronary vasodilatory response to hypoxia were observed, and metaboreflex activation during hypoxia caused a paradoxical reduction in coronary blood velocity in males but not females.