Elective Coronary Stenting Increases Fractional Flow Reserve in Other Arteries due to an Increase in Microvascular Resistance: Clinical Implications for Assessment of Multivessel Disease

Fractional Flow Reserve following Percutaneous Coronary Intervention

Fractional flow reserve (FFR) is routinely used to determine lesion severity prior to percutaneous coronary intervention (PCI). However, there is an increasing recognition that FFR may also be useful following PCI to identify mechanisms leading to restenosis and the need for repeat revascularization. Post-PCI FFR is associated with the presence and severity of stent under-expansion and may help identify peri-stent-related complications. FFR pullback may also unmask other functionally significant lesions within the target vessel that were not appreciable on angiography. Recent studies have confirmed the prognostic utility of performing routine post-PCI FFR and suggest possible interventional targets that would improve stent durability. In this review, we detail the theoretical basis underlying post-PCI FFR, provide practical tips to facilitate measurement, and discuss the growing evidence supporting its use.

Assessing the left main stem in the cardiac catheterization laboratory. What is "significant"? Function, imaging or both?

Revascularization of significant Left Main Stem (LMS) disease improves clinical outcomes. This can be achieved through either Coronary Artery Bypass Grafting or Percutaneous coronary intervention. Defining a significant stenosis of the LMS can be challenging and debatable, as most data have been derived using angiographic assessment alone, with a threshold of 50% luminal stenosis used as a marker of functional significance. The use of adjunctive technologies like Intravascular Ultrasound and Fractional Flow Reserve has improved our ability to accurately assess the anatomical severity and physiological significance of coronary artery stenoses, much more so, than can be achieved through conventional angiography alone. An improved assessment of LMS disease through these adjunctive techniques offers procedural and clinical benefits. Rather than focus on the preferred methods of revascularisation, this article aims to highlight the common pitfalls and misconceptions in the assessment of LMS stenoses. We also propose a simple algorithm for the assessment of LMS disease to help guide revascularisation decisions.

Diastolic Backward-Traveling Decompression (Suction) Wave Correlates With Simultaneously Acquired Indices of Diastolic Function and Is Reduced in Left Ventricular Stunning

Background—

Wave intensity analysis can distinguish proximal (propulsion) and distal (suction) influences on coronary blood flow and is purported to reflect myocardial performance and microvascular function. Quantifying the amplitude of the peak, backwards expansion wave (BEW) may have clinical utility. However, simultaneously acquired wave intensity analysis and left ventricular (LV) pressure–volume loop data, confirming the origin and effect of myocardial function on the BEW in humans, have not been previously reported.

Methods and Results—

Patients with single-vessel left anterior descending coronary disease and normal ventricular function (n=13) were recruited prospectively. We simultaneously measured LV function with a conductance catheter and derived wave intensity analysis using a pressure–low velocity guidewire at baseline and again 30 minutes after a 1-minute coronary balloon occlusion. The peak BEW correlated with the indices of diastolic LV function: LV dP/dt min ( r s =−0.59; P =0.002) and τ ( r s =−0.59; P =0.002), but not with systolic function. In 12 patients with paired measurements 30 minutes post balloon occlusion, LV dP/dt max decreased from 1437.1±163.9 to 1299.4±152.9 mm Hg/s (median difference, −110.4 [−183.3 to −70.4]; P =0.015) and τ increased from 48.3±7.4 to 52.4±7.9 ms (difference, 4.1 [1.3–6.9]; P =0.01), but basal average peak coronary flow velocity was unchanged, indicating LV stunning post balloon occlusion. However, the peak BEW amplitude decreased from −9.95±5.45 W·m –2 /s 2 ×10 5 to −7.52±5.00 W·m –2 /s 2 ×10 5 (difference 2.43×10 5 [0.20×10 5 to 4.67×10 5 ; P =0.04]).

Conclusions—

Peak BEW assessed by coronary wave intensity analysis correlates with invasive indices of LV diastolic function and mirrors changes in LV diastolic function confirming the origin of the suction wave. This may have implications for physiological lesion assessment after percutaneous coronary intervention.

Clinical Trial Registration—

URL: http://www.isrctn.org . Unique identifier: ISRCTN42864201.

Fundamentals in clinical coronary physiology: why coronary flow is more important than coronary pressure

Wide attention for the appropriateness of coronary stenting in stable ischaemic heart disease (IHD) has increased interest in coronary physiology to guide decision making. For many, coronary physiology equals the measurement of coronary pressure to calculate the fractional flow reserve (FFR). While accumulating evidence supports the contention that FFR-guided revascularization is superior to revascularization based on coronary angiography, it is frequently overlooked that FFR is a coronary pressure-derived estimate of coronary flow impairment. It is not the same as the direct measures of coronary flow from which it was derived, and which are critical determinants of myocardial ischaemia. This review describes why coronary flow is physiologically and clinically more important than coronary pressure, details the resulting limitations and clinical consequences of FFR-guided clinical decision making, describes the scientific consequences of using FFR as a gold standard reference test, and discusses the potential of coronary flow to improve risk stratification and decision making in IHD.

Impact of nonculprit vessel myocardial perfusion on outcomes of patients undergoing percutaneous coronary intervention for acute coronary syndromes: analysis from the ACUITY trial (Acute Catheterization and Urgent Intervention Triage Strategy)

OBJECTIVES

This study evaluated the impact of nonculprit vessel myocardial perfusion on outcomes of non-ST-segment elevation acute coronary syndromes (NSTE-ACS) patients.

BACKGROUND

ST-segment elevation myocardial infarction patients have decreased perfusion in areas remote from the infarct-related vessel. The impact of myocardial hypoperfusion of regions supplied by nonculprit vessels in NSTE-ACS patients treated with percutaneous coronary intervention (PCI) is unknown.

METHODS

The angiographic substudy of the ACUITY (Acute Catheterization and Urgent Intervention Triage Strategy) trial included 6,921 NSTE-ACS patients. Complete 3-vessel assessments of baseline coronary TIMI (Thrombolysis In Myocardial Infarction) flow grade and myocardial blush grade (MBG) were performed. We examined the outcomes of PCI-treated patients according to the worst nonculprit vessel MBG identified per patient.

RESULTS

Among the 3,826 patients treated with PCI, the worst nonculprit MBG was determined in 3,426 (89.5%) patients, including 375 (10.9%) MBG 0/1 patients, 475 (13.9%) MBG 2 patients, and 2,576 (75.2%) MBG 3 patients. Nonculprit MBG 0/1 was associated with worse baseline clinical characteristics. Patients with nonculprit MBG 0/1 versus MBG 3 had increased rates of 30-day (3.0% vs. 0.7%, p < 0.0001) and 1-year (4.4% vs. 1.0%, p < 0.0001) death. Similar results were found among patients with pre-procedural TIMI flow grade 3 in the culprit vessel, where nonculprit vessel MBG 0/1 (hazard ratio: 2.81 [95% confidence interval: 1.63 to 4.84], p = 0.0002) was the strongest predictor of 1-year mortality.

CONCLUSIONS

Reduced myocardial perfusion in an area supplied by a nonculprit vessel is associated with increased short- and long-term mortality rates in NSTE-ACS patients undergoing PCI. Furthermore, worst nonculprit MBG is able to risk-stratify patients with normal baseline flow of the culprit vessel.