Reactive hyperemia following coronary balloon angioplasty, but not dipyridamole-induced hyperemia, predicts resolution of exercise-induced ST-segment depression

Improvement in coronary haemodynamics after percutaneous coronary intervention: assessment using instantaneous wave-free ratio

Objective

To determine whether the instantaneous wave-free ratio (iFR) can detect improvement in stenosis significance after percutaneous coronary intervention (PCI) and compare this with fractional flow reserve (FFR) and whole cycle Pd/Pa.

Design

A prospective observational study was undertaken in elective patients scheduled for PCI with FFR ≤0.80. Intracoronary pressures were measured at rest and during adenosine-mediated vasodilatation, before and after PCI. iFR, Pd/Pa and FFR values were calculated using the validated fully automated algorithms.

Setting

Coronary catheter laboratories in two UK centres and one in the USA.

Patients

120 coronary stenoses in 112 patients were assessed. The mean age was 63±10 years, while 84% were male; 39% smokers; 33% with diabetes. Mean diameter stenosis was 68±16% by quantitative coronary angiography.

Results

Pre-PCI, mean FFR was 0.66±0.14, mean iFR was 0.75±0.21 and mean Pd/Pa 0.83±0.16. PCI increased all indices significantly (FFR 0.89±0.07, p<0.001; iFR 0.94±0.05, p<0.001; Pd/Pa 0.96±0.04, p<0.001). The change in iFR after intervention (0.20±0.21) was similar to ΔFFR 0.22±0.15 (p=0.25). ΔFFR and ΔiFR were significantly larger than resting ΔPd/Pa (0.13±0.16, both p<0.001). Similar incremental changes occurred in patients with a higher prevalence of risk factors for microcirculatory disease such as diabetes and hypertension.

Conclusions

iFR and FFR detect the changes in coronary haemodynamics elicited by PCI. FFR and iFR have a significantly larger dynamic range than resting Pd/Pa. iFR might be used to objectively document improvement in coronary haemodynamics following PCI in a similar manner to FFR.

Coronary flow reserve varies depending upon the location within the artery it is assessed and the TIMI myocardial perfusion grade: a PROTECT TIMI-30 analysis

Coronary flow reserve (CFR) is a measure of the capacity of the epicardial coronary artery and the microvasculature to achieve maximal blood flow in response to hyperemic stimulation. It is not known whether the CFR varies along the length of the artery. Likewise, the interaction between CFR and the thrombolysis in myocardial infarction (TIMI) myocardial perfusion grade (TMPG) is unknown. CFR was measured using the number of cineframes required for the contrast to traverse the same length of the coronary artery before and following the administration of intracoronary adenosine. Following percutaneous coronary intervention (PCI), CFR was assessed both proximal and distal to the lesion in 192 consecutive patients with non-ST-segment elevation acute coronary syndrome (NSTEACS) from the PROTECT TIMI-30 trial. TMPG was also assessed. The difference between the distal and proximal CFR for patients with TMPG 0/1 (n = 76) was 0.11 (95% CI 0.01-0.20, P = 0.026), while among those with TMPG 2/3 (n = 114) it was -0.02 (95% CI -0.09-0.06, P = 0.65). The difference in the CFR between the distal and proximal segments among patients with TMPG 0/1 and TMPG 2/3 was significant (P interaction = 0.044). Following PCI among patients with impaired TMPG (0/1) in the setting of NSTEACS, CFR varies significantly between the proximal and distal segment of coronary arteries and is associated with higher (greater) distal CFR.

Upregulation of ecto-5'-nucleotidase by rosuvastatin increases the vasodilator response to ischemia

3-Hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors (statins) are effective in the primary and secondary prevention of cardiovascular events. Although originally developed to improve lipid profile, statins have demonstrated a surplus of beneficial pleiotropic effects, including improved endothelial function, reduced inflammation, and increased tolerance to ischemia-reperfusion injury. In preclinical studies, increased ecto-5'-nucleotidase activity, the key enzyme in extracellular adenosine formation, plays an important role in these effects. Because human data are absent, we explored the effects of rosuvastatin on ecto-5'-nucleotidase activity and the clinical relevance of increased extracellular adenosine during ischemia in humans in vivo. The forearm vasodilator responses to 3 increasing periods of forearm ischemia (2, 5, and 13 minutes) were determined during placebo and caffeine (an adenosine receptor antagonist) infusion into the brachial artery. At the end of an 8-day treatment period with rosuvastatin (20 mg per day), this whole procedure was repeated. During both experiments, ecto-5'-nucleotidase activity was determined. Vasodilator responses are expressed as the percentage increase in forearm blood flow ratio from baseline. Rosuvastatin increased ecto-5'-nucleotidase activity by 49±17% and enhanced the vasodilator response after 2, 5, and 13 minutes of ischemia in the absence (146±19, 330±26, and 987±133 to 312±77, 566±107, and 1533±267) but not in the presence of caffeine (98±25, 264±54, and 727±111 versus 95±19, 205±34, and 530±62). Rosuvastatin increases extracellular formation of adenosine in humans in vivo probably by enhancing ecto-5'-nucleotidase activity. This action results in the improvement of reactive hyperemia and may further enhance the clinical benefit of statins, in particular in conditions of ischemia.