Clinical significance of the microvasculature in coronary syndromes

This thesis explores the role of coronary physiology in the diagnosis, management, and prognosis of chronic and acute coronary syndromes. Part A focuses on the procedural considerations of assessing coronary physiology invasively using pressure and flow measurements. The authors discuss the limitations of resting indices in evaluating coronary stenosis severity and the importance of performing physiological assessments meticulously. Moreover, they investigate the comprehensive diagnosis of chronic coronary syndromes and the insights provided by combined pressure and flow measurements. Also, the impact of percutaneous coronary intervention (PCI) on resolving myocardial ischemia in discordant stenoses based on the novel coronary-flow-capacity (CFC) concept is assessed. Part B focuses on microvascular function in acute coronary syndromes, particularly in patients with ST-segment elevation myocardial infarction (STEMI). The authors discuss the pathophysiology, diagnostic armamentarium, and treatment strategies related to microvasculature in patients with STEMI. They investigate the microvascular function in the acute event of myocardial infarction and how it restores following a successful primary percutaneous intervention. Overall, the thesis provides a comprehensive overview of the role of the coronary microcirculation in the diagnosis, management, and prognosis of chronic and acute coronary syndromes. The authors emphasize the importance of performing physiological assessments meticulously and highlight the limitations and challenges associated with current diagnostic methods. They also provide insights into the potential future directions for the field

Long-term outcomes of a Caucasian cohort presenting with acute coronary syndrome and/or out-of-hospital cardiac arrest caused by coronary spasm

Contains fulltext : 190517.pdf (publisher's version ) (Open Access)BACKGROUND: Coronary artery spasm may be the underlying mechanism in up to 10% of cases of acute coronary syndrome (ACS) and sudden cardiac death. Asian individuals exhibit a 3-times greater incidence of spasm than Caucasians; this is likely due to different types of mechanisms. Consequently, solid data is limited about the long-term prognosis in Caucasian patients presenting with ACS and/or out-of-hospital cardiac arrest (OHCA) caused by coronary spasm. METHODS: Between 2002 and 2015, thirty Caucasian patients with coronary artery spasm presenting with ACS (N = 29) and/or OHCA (N = 11) were enrolled in this prospective registry. Follow-up, consisting of regular outpatient visits, was conducted with a mean follow-up period of 7.5 +/- 3.3 years. Outcomes included presence of stable angina pectoris, recurrence of ACS, occurrence of implantable cardioverter defibrillator (ICD) shocks and death. RESULTS: The majority of patients (60%) remained asymptomatic during the entire follow-up period. At the end of the follow-up period only 3 patients still experienced stable angina (10%). Only 2 patients (7%) had a recurrent cardiac event, in which the ICD provided appropriate shock therapy. Half of the patients treated with stenting (N = 6), required re-interventions. CONCLUSION: Coronary spasm with ACS and/or OHCA in a Caucasian patient cohort has a relatively benign prognosis in the majority of patients in long-term follow-up, if treated appropriately with medical therapy. Both the role of ICD in OHCA secondary to coronary spasm, and the efficacy of stenting to treat vasospastic angina, warrant further study in large-sized prospective clinical trials

Mechanical ventilation-induced intrathoracic pressure distribution and heart-lung interactions

OBJECTIVE: Mechanical ventilation causes cyclic changes in the heart's preload and afterload, thereby influencing the circulation. However, our understanding of the exact physiology of this cardiopulmonary interaction is limited. We aimed to thoroughly determine airway pressure distribution, how this is influenced by tidal volume and chest compliance, and its interaction with the circulation in humans during mechanical ventilation. DESIGN: Intervention study. SETTING: ICU of a university hospital. PATIENTS: Twenty mechanically ventilated patients following coronary artery bypass grafting surgery. INTERVENTION: Patients were monitored during controlled mechanical ventilation at tidal volumes of 4, 6, 8, and 10 mL/kg with normal and decreased chest compliance (by elastic binding of the thorax). MEASUREMENTS AND MAIN RESULTS: Central venous pressure, airway pressure, pericardial pressure, and pleural pressure; pulse pressure variations, systolic pressure variations, and stroke volume variations; and cardiac output were obtained during controlled mechanical ventilation at tidal volume of 4, 6, 8, and 10 mL/kg with normal and decreased chest compliance. With increasing tidal volume (4, 6, 8, and 10 mL/kg), the change in intrathoracic pressures increased linearly with 0.9 ± 0.2, 0.5 ± 0.3, 0.3 ± 0.1, and 0.3 ± 0.1 mm Hg/mL/kg for airway pressure, pleural pressure, pericardial pressure, and central venous pressure, respectively. At 8 mL/kg, a decrease in chest compliance (from 0.12 ± 0.07 to 0.09 ± 0.03 L/cm H2O) resulted in an increase in change in airway pressure, change in pleural pressure, change in pericardial pressure, and change in central venous pressure of 1.1 ± 0.7, 1.1 ± 0.8, 0.7 ± 0.4, and 0.8 ± 0.4 mm Hg, respectively. Furthermore, increased tidal volume and decreased chest compliance decreased stroke volume and increased arterial pressure variations. Transmural pressure of the superior vena cava decreased during inspiration, whereas the transmural pressure of the right atrium did not change. CONCLUSIONS: Increased tidal volume and decreased chest wall compliance both increase the change in intrathoracic pressures and the value of the dynamic indices during mechanical ventilation. Additionally, the transmural pressure of the vena cava is decreased, whereas the transmural pressure of the right atrium is not changed

Microvascular dysfunction following ST-elevation myocardial infarction and its recovery over time

Item does not contain fulltextAIMS: It is unclear whether microvascular dysfunction following ST-elevation myocardial infarction (STEMI) is prognostic for long-term left ventricular function (LVF), and whether recovery of the microvasculature status is associated with LVF improvement. The aim of this study was to assess whether microvascular dysfunction in the infarct-related artery (IRA), as assessed by coronary flow reserve (CFR) within one week after PPCI, was associated with LVF at both four months and two years. METHODS AND RESULTS: In 62 patients, CFR and hyperaemic microvascular resistance index (HMRI) in the IRA were assessed by intracoronary Doppler flow measurements within one week and at four months. CMR was performed at the same time points and also at two years. CFR at baseline was associated with left ventricular ejection fraction (LVEF) at four months (beta=4.66, SE=2.10; p=0.03) and at two-year follow-up (beta=5.84, SE=2.45; p=0.02). HMRI was not associated with LVF. In large infarcts, absolute improvement of CFR in the first four months was associated with LVEF improvement (beta=5.09, SE=1.86, p=0.01). CONCLUSIONS: Microvascular dysfunction, assessed by CFR, in the subacute phase of STEMI is prognostic for LVEF at four months and two years. This underlines the pivotal role of microvascular dysfunction following STEMI

Phasic flow patterns of right versus left coronary arteries in patients undergoing clinical physiological assessment

BACKGROUND: Coronary blood flow in humans is known to be predominantly diastolic. Small studies in animals and humans suggest that this is less pronounced or even reversed in the right coronary artery (RCA). AIMS: This study aimed to characterise the phasic patterns of coronary flow in the left versus right coronary arteries of patients undergoing invasive physiological assessment. METHODS: We analysed data from the Iberian-Dutch-English Collaborators (IDEAL) study. A total of 482 simultaneous pressure and flow measurements from 301 patients were included in our analysis. RESULTS: On average, coronary flow was higher in diastole both at rest and during hyperaemia in both the RCA and LCA (mean diastolic-to-systolic velocity ratio [DSVR] was, respectively, 1.85±0.70, 1.76±0.58, 1.53±0.34 and 1.58±0.43 for LCA(rest), LCA(hyp), RCA(rest) and RCA(hyp), p<0.001 for between-vessel comparisons). Although the type of RCA dominance affected the DSVR magnitude (RCA(dom)=1.55±0.35, RCA(co-dom)=1.40±0.27, RCA(non-dom)=1.35; standard deviation not reported as n=3), systolic flow was very rarely predominant (DSVR was greater than or equal to 1.00 in 472/482 cases [97.9%] overall), with equal prevalence in the LCA. Stenosis severity or microvascular dysfunction had a negligible impact on DSVR in both the RCA and LCA (DSVR x hyperaemic stenosis resistance R(2) =0.018, p=0.03 and DSVR x coronary flow reserve R(2) <0.001, p=0.98). CONCLUSIONS: In patients with coronary artery disease undergoing physiological assessment, diastolic flow predominance is seen in both left and right coronary arteries. Clinical interpretation of coronary physiological data should therefore not differ between the left and the right coronary systems