Impact of Alpha- and Beta-Adrenergic Receptor Blockers on Fractional Flow Reserve and Index of Microvascular Resistance

End-diastolic velocity mediates the relationship between renal resistive index and the risk of death

OBJECTIVE

Renal resistive index predicts the risk of death in many populations but the mechanism linking renal resistive index and death remains elusive. Renal resistive index is derived from end-diastolic velocity (EDV) and peak systolic velocity (PSV). However, the predictive value of EDV or PSV considered alone is unknown.

METHODS

We conducted a retrospective analysis of 2362 consecutive patients who received a kidney transplant from 1985 to 2017. EDV and PSV were measured at 3 months after transplantation, renal resistive index was calculated, and the risk of death was assessed [median follow-up: 6.25 years (0.25-29.15); total observation period: 13 201 patient-years].

RESULTS

Doppler indices were available in 1721 of 2362 (78.9%) patients (exclusions: 113 who died or returned to dialysis before, 427 with no Doppler studies, 27 with renal artery stenosis, 74 missing values). Among them, 279 (16.4%) had diabetes before transplantation. Mean age was 51.5 ± 14.7, 1097 (63.7%) were male. During follow-up, 217 of 1721 (12.6%) patients died. Renal resistive index and EDV shared many determinants (notably systolic, diastolic and pulse pressure, recipient age and diabetes) unlike renal resistive index and PSV. EDV used as a binary [lowest tertile vs. higher values: (hazard ratio: 2.57 (1.96-3.36), P  < 0.001)] and as a continuous (the lower EDV, the greater the risk of death) variable was significantly associated with the risk of death. This finding was confirmed in multivariable analyses. Prediction of similar magnitude was found for renal resistive index. No association was found between PSV used as a binary or a continuous variable and the risk of death.

CONCLUSION

Low EDV explains high renal resistive index, and the mechanism-linking renal resistive index to the risk of death is through low EDV.

Pathophysiology and mechanisms of Acute Coronary Syndromes: athero-thrombosis, immune-inflammation and beyond

INTRODUCTION

The pathophysiology of atherosclerosis and its acute complications, such as the Acute Coronary Syndromes (ACS), is continuously under investigation. Immunity and inflammation seem to play a pivotal role in promoting formation and grow of atherosclerotic plaques. At the same time, plaque rupture followed by both platelets' activation and coagulation cascade induction lead to intracoronary thrombus formation. Although these phenomena might be considered responsible of about 90% of ACS, in up to 5-10% of acute syndromes a non-obstructive coronary artery disease (MINOCA) might be documented. This paper gives an overview on athero-thrombosis and immuno-inflammation processes involved in ACS pathophysiology also emphasizing the pathological mechanisms potentially involved in MINOCA.

AREAS COVERED

The relationship between immuno-inflammation and atherothrombosis is continuously updated by recent findings. At the same time, pathophysiology of MINOCA still remains a partially unexplored field, stimulating the research of potential links between these two aspects of ACS pathophysiology.

EXPERT OPINION

Pathophysyiology of ACS has been extensively investigated; however, several grey areas still remain. MINOCA represents one of these areas. At the same time, many aspects of immune-inflammation processes are still unknown. Thus, research should be continued to shed a brighter light on both these sides of "ACS" moon.

Fractional flow reserve in patients with reduced ejection fraction

AIMS

Fractional flow reserve (FFR) has never been investigated in patients with reduced ejection fraction and associated coronary artery disease (CAD). We evaluated the impact of FFR on the management strategies of these patients and related outcomes.

METHODS AND RESULTS

From 2002 to 2010, all consecutive patients with left ventricular ejection fraction (LVEF) ≤50% undergoing coronary angiography with ≥1 intermediate coronary stenosis [diameter stenosis (DS)% 50-70%] treated based on angiography (Angiography-guided group) or according to FFR (FFR-guided group) were screened for inclusion. In the FFR-guided group, 433 patients were matched with 866 contemporary patients of the Angiography-guided group. For outcome comparison, 617 control patients with LVEF >50% were included. After FFR, stenotic vessels per patient were significantly downgraded compared with the Angiography-guided group (1.43 ± 0.98 vs. 1.97 ± 0.84; P < 0.001). This was associated with lower revascularization rate (52% vs. 62%; P < 0.001) in the FFR-guided vs. the Angiography-guided group. All-cause death at 5 years of follow-up was significantly lower in the FFR-guided as compared with Angiography-guided group [22% vs. 31%. HR (95% CI) 0.64 (0.51-0.81); P < 0.001]. Similarly, rate of major adverse cardiovascular and cerebrovascular events (MACCE: composite of all-cause death, myocardial infarction, revascularization, and stroke) was significantly lower in the FFR-guided group [40% vs. 46% in the Angiography-guided group. HR (95% CI) 0.81 (0.67-0.97); P = 0.019]. Higher rates of death and MACCE were observed in patients with reduced LVEF compared with the control cohort.

CONCLUSIONS

In patients with reduced LVEF and CAD, FFR-guided revascularization was associated with lower rates of death and MACCE at 5 years as compared with the Angiography-guided strategy. This beneficial impact was observed in parallel with less coronary artery bypass grafting and more patients deferred to percutaneous coronary intervention or medical therapy.

Preprocedural β-Blockers in the Functional Assessment of Intermediate Coronary Lesions by Instantaneous Wave-Free Ratio

AIM

Instantaneous wave-free ratio (iFR) has emerged as the strategy of choice for the assessment of intermediate coronary lesions. The impact of preprocedural β-blockers therapy on the iFR was the aim of this study.

METHODS

We included patients undergoing functional assessment of intermediate (40%-70%) coronary lesions in 2 centers. The iFR measurement was performed by pressure-recording guidewire and calculated at the core laboratory using the manufacturers' dedicated software. Minimal luminal diameter, reference diameter, percent diameter stenosis, and length of the lesion were measured. Positive iFR was considered for values <0.90.

RESULTS

We included 197 patients undergoing functional evaluation of 223 coronary lesions. Patients on β-blockers (69%) had more frequently hypertension (P = .05); previous myocardial infarction (P = .01); therapy with clopidogrel (P = .02), statins, and aspirin; and acute coronary syndrome at presentation (P < .001, respectively). Mean iFR values were slightly higher in patients on β-blockers (0.94 ± 0.06 vs 0.92 ± 0.06, P = .11). The rate of positive iFR was significantly lower with β-blockers (14.9% vs 27.5%, P = .04). On multivariate analysis, β-blockers use was a predictor of the significance of coronary stenoses (odds ratio [OR] = 0.48; 95% CI = 0.23-0.98; P = .05) together with lesion length (OR = 1.04; 95% CI = 1.01-1.07; P = .007).

CONCLUSION

Among patients undergoing iFR, preprocedural β-blockers are associated with higher absolute values and a lower rate of positive iFR.

Coronary Artery Bypass Grafting or Fractional Flow Reserve–Guided Percutaneous Coronary Intervention in Diabetic Patients With Multivessel Disease

Background:

In diabetic patients with multivessel coronary artery disease, coronary artery bypass grafting (CABG) has shown long-term benefits over percutaneous coronary intervention (PCI). Physiology-guided PCI has shown to improve clinical outcomes in multivessel coronary artery disease, though its impact in diabetic patients has never been investigated. We evaluated long-term clinical outcomes of diabetic patients with multivessel coronary artery disease treated with fractional flow reserve (FFR)–guided PCI compared with CABG.

Methods:

From 2010 to 2018, 4622 diabetic patients undergoing coronary angiography were screened for inclusion. The inclusion criterion was the presence of at least 2-vessel disease defined as with diameter stenosis ≥50%, in which at least 1 intermediate stenosis (diameter stenosis, 30%–70%) was treated or deferred according to FFR. Inverse probability of treatment weighting analysis was used to account for baseline differences with a contemporary cohort of patients treated with CABG. The primary end point was major adverse cardiovascular and cerebrovascular events, defined as all-cause death, myocardial infarction, revascularization, or stroke.

Results:

A total of 418 patients were included in the analysis. Among them, 209 patients underwent CABG and 209 FFR-guided PCI. At 5 years, the incidence of major adverse cardiovascular and cerebrovascular events was higher in the FFR-guided PCI versus the CABG group (44.5% versus 31.9%; hazard ratio, 1.60 [95% CI, 1.15–2.22]; P =0.005). No difference was found in the composite of all-cause death, myocardial infarction, or stroke (28.8% versus 27.5%; hazard ratio, 1.05 [95% CI, 0.72–1.53]; P =0.81). Repeat revascularization was more frequent with FFR-guided PCI (24.9% versus 8.2%; hazard ratio, 3.51 [95% CI, 1.93–6.40]; P <0.001).

Conclusions:

In diabetic patients with multivessel coronary artery disease, CABG was associated with a lower rate of major adverse cardiovascular and cerebrovascular events compared with FFR-guided PCI, driven by a higher rate of repeat revascularization. At 5-year follow-up, no difference was observed in the composite of all-cause death, myocardial infarction, or stroke between CABG and FFR-guided PCI.

Graphic Abstract:

A graphic abstract is available for this article.

Correlation between Angiographic and Physiologic Evaluation of Coronary Artery Narrowings in Patients With Aortic Valve Stenosis

We aimed to assess the correlation between angiographic and physiologic evaluation of coronary lesions in aortic stenosis (AS) patients presenting with intermediate coronary stenoses at the angiography. From 2002 to 2010, we included 163 patients from 2 centers with both AS and coronary artery disease (CAD), matched by age and gender with 163 contemporary patients with CAD alone. With both quantitative coronary angiography and fractional flow reserve (FFR), we assessed 259 coronary stenoses in the AS + CAD group, and 256 in the CAD alone group. A significant correlation was found between diameter stenosis (DS) and FFR in both groups, although this was significantly stronger in the AS + CAD than in the CAD alone group (R = -0.63 vs -0.44, p <0.01). Likewise, the correlation between minimum lumen diameter and FFR was stronger in the AS + CAD than in the CAD alone group (R = -0.54 vs -0.41, p = 0.05). Receiver operator characteristic curves analysis showed that DS was a better predictor of hemodynamically significant coronary stenoses (FFR ≤0.8) in the AS + CAD rather than in the CAD alone group (area under the curve = 0.83 vs 0.67, p <0.01). With 50% DS cut-off value, the sensitivity, specificity, and accuracy was 77%, 66%, and 70% in the AS + CAD group versus 59%, 63%, and 61% in the CAD alone group. In both groups, the diagnostic accuracy of DS in predicting FFR was higher in the right and circumflex coronary artery compared with the left anterior descending artery (LAD), although this was only statistically significant in the AS + CAD group (area under the curve 0.88 in the right and circumflex coronary artery vs 0.76 in LAD, p = 0.03). In conclusion, the correlation between the angiographic and hemodynamic significance of coronary stenoses is modest in AS patients. The assessment of CAD severity solely based on angiography poorly predicts the hemodynamic significance of the coronary stenosis especially when these are located in the LAD.

Invasive minimal Microvascular Resistance Is a New Index to Assess Microcirculatory Function Independent of Obstructive Coronary Artery Disease

BACKGROUND

Coronary microcirculatory dysfunction portends a poor cardiovascular outcome. Invasive assessment of microcirculatory dysfunction by coronary flow reserve (CFR) and hyperemic microvascular resistance (HMR) is affected by coronary artery disease (CAD). In this study we propose minimal microvascular resistance (mMR) as a new measure of microcirculatory dysfunction and aim to determine whether mMR is influenced by CAD.

METHODS AND RESULTS

We obtained 482 simultaneous measurements of intracoronary Doppler flow velocity and pressure. The mMR is defined as the ratio between distal coronary pressure and flow velocity during the hyperemic wave-free period. Measurements were divided into 2 cohorts. Cohort 1 was a paired analysis involving 81 pairs with a vessel with and without CAD to investigate whether HMR, CFR, and mMR are modulated by CAD. CFR was lower, and HMR was higher, in vessels with CAD than in vessels without CAD: 2.12±0.79 versus 2.56±0.63 mm Hg·cm-1·s, P<0.001, and 2.61±1.22 versus 2.31±0.89 mm Hg·cm-1·s, P=0.04, respectively. mMR was equal in vessels with and without CAD: 1.54±0.77 versus 1.53±0.57 mm Hg·cm-1·s, P=0.90. Differences for CFR occurred when FFR was 0.60 to 0.80 or ≤0.60 but not when FFR ≥0.80. For HMR, the difference occurred only when FFR ≤0.60. For mMR, no difference was observed in any FFR stratum. Cohort 2 was used for validation and showed significant relationships for CFR and HMR with FFR: Pearson r=0.488, P<0.001 and -0.159, P=0.03, respectively; mMR had no association with FFR: Pearson r=0.055; P=0.32.

CONCLUSIONS

mMR is a novel index to assess microcirculatory dysfunction and is not modified by the presence of obstructive CAD.

Fractional Flow Reserve-Guided Revascularization in Patients With Aortic Stenosis

Fractional flow reserve (FFR) has never been investigated in patients with aortic stenosis (AS). From 2002 to 2010, we identified 106 patients with AS and coronary artery disease with at least one intermediate lesion treated according to FFR guidance. We matched 212 contemporary control patients with AS in which revascularization was decided on angiography only. More patients in the FFR-guided group underwent percutaneous coronary intervention (24% vs 13%; p = 0.019), whereas there was a trend toward less coronary artery bypass grafting (CABG) performed. After FFR, the number of diseased vessels was downgraded within the FFR-guided group (from 1.85 ± 0.97 to 1.48 ± 1; p <0.01) and compared with the angio-guided group (1.48 ± 1 vs 1.8 ± 0.97; p <0.01). Less aortic valve replacement was reported in the FFR-guided group (46% vs 57%; p = 0.056). In patients who underwent CABG, less venous conduits (0.5 ± 0.69 vs 0.73 ± 0.76; p = 0.05) and anastomoses (0.61 ± 0.85 vs 0.94 ± 1; p = 0.032) were necessary in the FFR-guided group. Up to 5 years, we found no difference in major adverse cardiac events (38% vs 39%; p = 0.98), overall death (32% vs 31%; p = 0.68), nonfatal myocardial infarction (2% vs 2%; p = 0.79), and revascularization (8% vs 7%; p = 0.76) between the 2 groups. In conclusion, FFR guidance impacts the management of selected patients with moderate or severe AS and coronary artery disease by resulting into deferral of aortic valve replacement, more patients treated with percutaneous coronary intervention, and in patients treated with CABG, into less venous grafts and anastomoses without increasing adverse event rates up to 5 years.

Prediction of Flow-Limiting Fractional Flow Reserve in Patients With Stable Coronary Artery Disease Based on Quantitative Myocardial Perfusion Imaging

Although fractional flow reserve (FFR) and myocardial perfusion imaging (MPI) findings fundamentally differ, several cohort studies have revealed that these findings correlate. Here, we investigated whether flow-limiting FFR could be predicted from adenosine stress thallium-201 MPI with single-photon emission computed tomography (SPECT) findings derived from 84 consecutive, prospectively identified patients with stable coronary artery disease and 212 diseased vessels. Among them, FFR was measured in 136 diseased vessels (64%). The findings were compared with regional perfusion abnormalities including stress total perfusion defect (TPD) - rest TPD determined using quantitative perfusion single-photon emission computed tomography software. The FFR inversely correlated the most accurately with stress TPD - rest TPD (r = -0.552, p <0.001). Predictors of major vessels of interest comprising FFR <0.80, included stress TPD - rest TPD, the transient ischemic dilation ratio, left ventricular ejection fraction at rest and beta blockers for left anterior descending artery (LAD) regions, and stress TPD - rest TPD, left ventricular mass, left ventricular ejection fraction at rest, right coronary artery lesions, the transient ischemic dilation ratio, and age for non-LAD regions. The diagnostic accuracy of formulas to predict major vessels of interest with FFR <0.80 was high (sensitivity, specificity and accuracy for LAD and non-LAD: 84%, 87% and 86%, and 75%, 93% and 87%, respectively). In conclusion, although somewhat limited by a sample size and a single-center design, flow-limiting FFR could be predicted from MPI findings with a defined probability. A cohort study might validate our results and provide a novel adjunctive tool with which to diagnose functionally significant coronary artery disease from MPI findings.

The present day potential role of fractional flow reserve-guided coronary artery bypass graft surgery

The favorable impact of fractional flow reserve measurements on the decision-making and overall outcomes of percutaneous coronary artery intervention is well established. However, the clinical application of fractional flow reserve in surgical revascularizations is still debated. The purpose of this article is to provide a comprehensive review on the current potential role of fractional flow reserve guidance in coronary artery bypass grafting.