Impact of coronary artery disease on contractile function and ventricular-arterial coupling during exercise: Simultaneous assessment of left-ventricular pressure-volume and coronary pressure and flow during cardiac catheterization.

Coronary artery disease (CAD) can adversely affect left ventricular (LV) performance during exercise by impairment of contractile function in the presence of increasing afterload. By performing invasive measures of LV pressure-volume and coronary pressure and flow during exercise, we sought to accurately measure this with comparison to the control group. Sixteen patients, with CCS class >II angina and CAD underwent invasive simultaneous measurement of left ventricular pressure-volume and coronary pressure and flow velocity during cardiac catheterization. Measurements performed at rest were compared with peak exercise using bicycle ergometry. The LV contractile function was measured invasively using the end-systolic pressure-volume relationship, a load independent marker of contractile function (Ees). Vascular afterload forces were derived from the ratio of LV end-systolic pressure to stroke volume to generate arterial elastance (Ea). These were combined to assess cardiovascular performance (ventricular-arterial [VA] coupling ratio [Ea/Ees]). Eleven patients demonstrated flow-limiting (FL) CAD (hyperemic Pd/Pa <0.80; ST-segment depression on exercise); five patients without flow-limiting (NFL) CAD served as the control group. Exercise in the presence of FL CAD was associated impairment of Ees, increased Ea, and deterioration of VA coupling. In the control cohort, exercise was associated with increased Ees and improved VA coupling. The backward compression wave energy directly correlated with the magnitude contraction as measured by dP/dTmax (r = 0.88, p = 0.004). This study demonstrates that in the presence of flow-limiting CAD, exercise to maximal effort can lead to impairment of LV contractile function and a deterioration in VA coupling compared to a control cohort.

Rationale and design of: A Randomized tRial of Expedited transfer to a cardiac arrest center for non-ST elevation out-of-hospital cardiac arrest: The ARREST randomized controlled trial.

BACKGROUND: Out-of-hospital cardiac arrest (OHCA) is a global public health issue. There is wide variation in both regional and inter-hospital survival rates from OHCA and overall survival remains poor at 7%. Regionalization of care into cardiac arrest centers (CAC) improves outcomes following cardiac arrest from ST elevation myocardial infarction (STEMI) through concentration of services and greater provider experience. The International Liaison Committee on Resuscitation (ILCOR) recommends delivery of all post-arrest patients to a CAC, but that randomized controlled trials are necessary in patients without ST elevation (STE). METHODS/DESIGN: Following completion of a pilot randomized trial to assess safety and feasibility of conducting a large-scale randomized controlled trial in patients following OHCA of presumed cardiac cause without STE, we present the rationale and design of A Randomized tRial of Expedited transfer to a cardiac arrest center for non-ST elevation OHCA (ARREST). In total 860 patients will be enrolled and randomized (1:1) to expedited transfer to CAC (24/7 access to interventional cardiology facilities, cooling and goal-directed therapies) or to the current standard of care, which comprises delivery to the nearest emergency department. Primary outcome is 30-day all-cause mortality and secondary outcomes are 30-day and 3-month neurological status and 3, 6 and 12-month mortality. Patients will be followed up for one year after enrolment. CONCLUSION: Post-arrest care is time-critical, requires a multi-disciplinary approach and may be more optimally delivered in centers with greater provider experience. This trial would help to demonstrate if regionalization of post-arrest care to CACs reduces mortality in patients without STE, which could dramatically reshape emergency care provision.

Assessment of coronary artery stenosis severity and location: quantitative analysis of transmural perfusion gradients by high-resolution MRI versus FFR.

OBJECTIVES: This study sought to test the hypothesis that transmural perfusion gradients (TPG) on adenosine stress myocardial perfusion cardiac magnetic resonance (CMR) predict hemodynamically significant coronary artery disease (CAD) as defined by fractional flow reserve (FFR). BACKGROUND: Myocardial ischemia affects the subendocardial layers of the left ventricular myocardium earlier and more severely than the outer layers, and the identification of TPG should be sensitive and specific for the diagnosis of CAD. Previous studies have shown that high spatial resolution myocardial perfusion CMR allows quantitation of TPG between the subendocardium and the subepicardium. METHODS: Sixty-seven patients (53 men, age 61 ± 9 years) underwent coronary angiography and high-resolution (1.2 × 1.2-mm in-plane) adenosine stress perfusion CMR at 3.0-T. TPG was calculated for 3 coronary territories. Visual analysis was performed to identify myocardial ischemia. FFR was measured in all vessels with ≥50% severity stenosis. FFR <0.8 was considered hemodynamically significant. In a training group of 30 patients, the optimal threshold of TPG to detect significant CAD was determined (Group 1). This threshold was then tested prospectively in the remaining 37 patients (Group 2). RESULTS: In Group 1, a 20% TPG provided the best diagnostic threshold on both per-segment and per-patient analysis. Applied to Group 2, this threshold yielded a sensitivity of 0.78, specificity of 0.94, and area under the curve of 0.86 for the detection of CAD in a per-segment analysis and of 0.89, 0.83, and 0.86 in a per-patient analysis, respectively. TPG had a similar diagnostic accuracy to visual assessment. Linear regression analysis showed a relationship between TPG and FFR values, with r = 0.63 (p < 0.001). CONCLUSIONS: The quantitative analysis of transmural perfusion gradients on high-resolution myocardial perfusion CMR accurately predicts hemodynamically significant CAD as defined by FFR. A TPG diagnostic threshold of 20% is as accurate as visual assessment.