A double-blind, randomised, placebo-controlled trial of the coronary sinus Reducer in refractory angina: design and rationale of the ORBITA-COSMIC trial

The coronary sinus Reducer (CSR) is an hourglass-shaped device which creates an artificial stenosis in the coronary sinus. Whilst placebo-controlled data show an improvement in angina, these results are unreplicated and are the subject of further confirmatory research. The mechanism of action of this unintuitive therapy is unknown. The Coronary Sinus Reducer Objective Impact on Symptoms, MRI Ischaemia, and Microvascular Resistance (ORBITA-COSMIC) trial is a randomised, placebo-controlled, double-blind trial investigating the efficacy of the CSR. Patients with (i) established epicardial coronary artery disease, (ii) angina on maximally tolerated antianginal medication, (iii) evidence of myocardial ischaemia and (iv) no further options for percutaneous coronary intervention or coronary artery bypass grafting will be enrolled. Upon enrolment, angina and quality-of-life questionnaires, treadmill exercise testing and quantitative stress perfusion cardiac magnetic resonance (CMR) imaging will be performed. Participants will record their symptoms daily on a smartphone application throughout the trial. After a 2-week symptom assessment phase, participants will be randomised in the cardiac catheterisation laboratory to CSR or a placebo procedure. After 6 months of blinded follow-up, all prerandomisation tests will be repeated. A prespecified subgroup will undergo invasive coronary physiology assessment at prerandomisation and follow-up. The primary outcome is stress myocardial blood flow on CMR. Secondary outcomes include angina frequency, quality of life and treadmill exercise time. (ClinicalTrials.gov: NCT04892537).

A Placebo-Controlled Trial of Percutaneous Coronary Intervention for Stable Angina

BACKGROUND

Percutaneous coronary intervention (PCI) is frequently performed to reduce the symptoms of stable angina. Whether PCI relieves angina more than a placebo procedure in patients who are not receiving antianginal medication remains unknown.

METHODS

We conducted a double-blind, randomized, placebo-controlled trial of PCI in patients with stable angina. Patients stopped all antianginal medications and underwent a 2-week symptom assessment phase before randomization. Patients were then randomly assigned in a 1:1 ratio to undergo PCI or a placebo procedure and were followed for 12 weeks. The primary end point was the angina symptom score, which was calculated daily on the basis of the number of angina episodes that occurred on a given day, the number of antianginal medications prescribed on that day, and clinical events, including the occurrence of unblinding owing to unacceptable angina or acute coronary syndrome or death. Scores range from 0 to 79, with higher scores indicating worse health status with respect to angina.

RESULTS

A total of 301 patients underwent randomization: 151 to the PCI group and 150 to the placebo group. The mean (±SD) age was 64±9 years, and 79% were men. Ischemia was present in one cardiac territory in 242 patients (80%), in two territories in 52 patients (17%), and in three territories in 7 patients (2%). In the target vessels, the median fractional flow reserve was 0.63 (interquartile range, 0.49 to 0.75), and the median instantaneous wave-free ratio was 0.78 (interquartile range, 0.55 to 0.87). At the 12-week follow-up, the mean angina symptom score was 2.9 in the PCI group and 5.6 in the placebo group (odds ratio, 2.21; 95% confidence interval, 1.41 to 3.47; P<0.001). One patient in the placebo group had unacceptable angina leading to unblinding. Acute coronary syndromes occurred in 4 patients in the PCI group and in 6 patients in the placebo group.

CONCLUSIONS

Among patients with stable angina who were receiving little or no antianginal medication and had objective evidence of ischemia, PCI resulted in a lower angina symptom score than a placebo procedure, indicating a better health status with respect to angina. (Funded by the National Institute for Health and Care Research Imperial Biomedical Research Centre and others; ORBITA-2 ClinicalTrials.gov number, NCT03742050.).

Invasive Detection of Coronary Microvascular Dysfunction: How It Began, and Where We Are Now

The landscape of interventional cardiology is ever evolving. Contemporary practice has shifted from a stenosis-centred approach to the total characterisation of both the epicardial and microcirculatory vessels. Microcirculatory dysfunction plays an important role in the pathophysiology of acute and chronic coronary syndromes, and characterisation of the microcirculation has important clinical consequences. Accordingly, the invasive diagnosis of microcirculatory dysfunction is becoming a key feature of the interventional cardiologist's toolkit. This review focuses on the methodology underpinning the invasive diagnosis of microvascular dysfunction and highlights the indices that have arisen from these methodologies.

Changes in absolute flow, myocardial resistance and FFR after chronic total occlusion percutaneous coronary intervention

BACKGROUND

Randomised studies of percutaneous coronary intervention (PCI) in patients with chronic total occlusion (CTO) have shown inconsistent outcomes, suggesting incomplete understanding of this cohort and their coronary physiology. To address this shortcoming, we designed a prospective observational study to measure the recovery of absolute coronary blood flow following successful CTO PCI Aims: We sought to identify patient and procedural characteristics associated with a favourable physiological outcome after CTO PCI.

METHODS

Consecutive patients with a CTO subtending viable myocardium underwent PCI utilising contemporary techniques and the hybrid algorithm. Immediately after PCI, and at 3-month follow-up, physiological measurements were performed utilising continuous thermodilution.

RESULTS

A total of 81 patients were included with a mean age 63.6±8.9 years, and 66 (81.5%) were male. Physiological measurements of absolute coronary blood flow in the CTO vessel increased by 30% (p<0.001) and microvascular resistance reduced by 16% (p<0.001) from immediately post-CTO PCI to follow-up assessment. Fractional flow reserve increased by 0.02 (p=0.015) in the same period. Prior coronary artery bypass graft (CABG) and a higher estimated glomerular filtration rate (eGFR) were associated with a larger change in absolute flow. An extraplaque strategy was associated with a smaller change in absolute flow.

CONCLUSIONS

Post-CTO PCI, there is a continued augmentation in absolute coronary blood flow and reduction in microvascular resistance from baseline to follow-up at 3 months. Prior CABG and a higher baseline eGFR were predictors of a larger change in absolute coronary flow, whilst an extraplaque final wire path strategy predicted a smaller change. Lastly, the patient characteristics and comorbidities had a larger influence than procedural factors on the observed change in absolute flow.

Feasibility of early waking cardiac arrest patients whilst receiving therapeutic hypothermia: The therapeutic hypothermia and early waking (THAW) trial

AIM

To determine the safety and feasibility of an early (12 h) waking and extubation protocol for out-of-hospital cardiac arrest (OHCA) patients receiving targeted temperature management (TTM).

METHODS

This was a single-centre, prospective, non-randomised, observational, safety and feasibility pilot study which included successfully resuscitated OHCA patients, of presumed cardiac cause. Inclusion criteria were: OHCA patients aged over 18 years with a return of spontaneous circulation, who were going to receive TTM33 (TTM at 33 °C for 24 h and prevention of hyperthermia for 72 h) as part of their post cardiac arrest care. Clinical stability was measured against physiological and neurological parameters as well as clinical assessment.

RESULTS

50 consecutive patients were included (median age 65.5 years, 82% male) in the study. Four (8%) patients died within the first twelve hours and were excluded from the final cohort (n = 46). Twenty-three patients (46%) were considered clinically stable and suitable for early waking based on the intention to treat analysis; 12 patients were extubated early based on a variety of clinical factors (21.4 ± 8.6 h) whilst continuing to receive TTM33 with a mean core temperature of 34.2 °C when extubated. Of these, five patients were discharged from the intensive care unit (ICU) <48 h after admission with a mean ICU length of stay 1.8 ± 0.4 days. Twenty-eight patients (56%) were discharged from the ICU with a modified Rankin Score of 0-2. The overall intra-hospital mortality was 50% (n = 25).

CONCLUSIONS

It is safe and feasible to wake selected comatose OHCA patients at 12 h, allowing for earlier positive neuro-prognostication and reduced ICU stay.

Early targeted brain COOLing in the cardiac CATHeterisation laboratory following cardiac arrest (COOLCATH)

INTRODUCTION

Trials demonstrate significant clinical benefit in patients receiving therapeutic hypothermia (TH) after cardiac arrest. However, incidence of mortality and morbidity remains high in this patient group. Rapid targeted brain hypothermia induction, together with prompt correction of the underlying cause may improve outcomes in these patients. This study investigates the efficacy of Rhinochill, an intranasal cooling device over Blanketrol, a surface cooling device in inducing TH in cardiac arrest patients within the cardiac catheter laboratory.

METHODS

70 patients were randomized to TH induction with either Rhinochill or Blanketrol. Primary outcome measures were time to reach tympanic ≤34 °C from randomisation as a surrogate for brain temperature and oesophageal ≤34 °C from randomisation as a measurement of core body temperature. Secondary outcomes included first hour temperature drop, length of stay in intensive care unit, hospital stay, neurological recovery and all-cause mortality at hospital discharge.

RESULTS

There was no difference in time to reach ≤34 °C between Rhinochill and Blanketrol (Tympanic ≤34 °C, 75 vs. 107 mins; p=0.101; Oesophageal ≤34 °C, 85 vs. 115 mins; p=0.151). Tympanic temperature dropped significantly with Rhinochill in the first hour (1.75 vs. 0.94 °C; p<0.001). No difference was detected in any other secondary outcome measures. Catheter laboratory-based TH induction resulted in a survival to hospital discharge of 67.1%.

CONCLUSION

In this study, Rhinochill was not found to be more efficient than Blanketrol for TH induction, although there was a non-significant trend in favour of Rhinochill that potentially warrants further investigation with a larger trial.

Activation of bovine endothelial thromboxane receptors triggers release of prostacyclin but not EDRF

OBJECTIVE

The aim was to examine the capacity of U46619 (a stable thromboxane A2 mimetic) to mediate release of endothelium derived relaxing factor (EDRF) from bovine aortic endothelial cells, and compare the response to the U46619 dependent release of prostacyclin (PGI2).

METHODS

Bovine aortic endothelial cells (AG4762) were cultured in vitro on microcarrier beads, which were then loaded onto a column and perfused. The cells were challenged with U46619, bradykinin, or the Ca2+ ionophore ionomycin in the perfusate, and measurements made of the release of 6-oxo-PGF1 alpha (the stable hydrolysis product of PGI2, measured by radioimmunoassay) and EDRF (bioassay). Cells were also cultured on glass cover slips, loaded with Fura 2-AM, and measurements made of the rise in intracellular Ca2+ after challenge with U46619, bradykinin or ionomycin.

RESULTS

U46619 triggered release of 6-oxo-PGF1 alpha but not EDRF from AG4762 cells, contrasting with bradykinin which released both 6-oxo-PGF1 alpha and EDRF. Ionomycin had little or no capacity to mimic and trigger release of 6-oxo-PGF1 alpha, although ionomycin mediated large increases in intracellular Ca2+. In contrast, staurosporine (a putative inhibitor of protein kinase C) substantially inhibited the U46619 and bradykinin dependent release of 6-oxo-PGF1 alpha.

CONCLUSIONS

In contrast to bradykinin linked receptors on AG4762 endothelial cells, which are coupled to the release of both prostacyclin and EDRF, activation of thromboxane A2 receptors on these cells selectively triggers release of PGI2 but not EDRF. Further, based on the distinct effects of ionomycin and staurosporine, it appears that agonist stimulated PGI2 release from these cells is mediated predominantly by protein kinase C, rather than by rises in intracellular Ca2+. This observation contrasts with previously described mechanisms of PGI2 release from endothelium obtained from other sources.