Challenges and Burdens in the Coronary Artery Disease Care Pathway for Patients Undergoing Percutaneous Coronary Intervention: A Contemporary Narrative Review.

Clinical and economic burdens exist within the coronary artery disease (CAD) care pathway despite advances in diagnosis and treatment and the increasing utilization of percutaneous coronary intervention (PCI). However, research presenting a comprehensive assessment of the challenges across this pathway is scarce. This contemporary review identifies relevant studies related to inefficiencies in the diagnosis, treatment, and management of CAD, including clinician, patient, and economic burdens. Studies demonstrating the benefits of integration and automation within the catheterization laboratory and across the CAD care pathway were also included. Most studies were published in the last 5-10 years and focused on North America and Europe. The review demonstrated multiple potentially avoidable inefficiencies, with a focus on access, appropriate use, conduct, and follow-up related to PCI. Inefficiencies included misdiagnosis, delays in emergency care, suboptimal testing, longer procedure times, risk of recurrent cardiac events, incomplete treatment, and challenges accessing and adhering to post-acute care. Across the CAD pathway, this review revealed that high clinician burnout, complex technologies, radiation, and contrast media exposure, amongst others, negatively impact workflow and patient care. Potential solutions include greater integration and interoperability between technologies and systems, improved standardization, and increased automation to reduce burdens in CAD and improve patient outcomes.

Simplified Assessment of the Index of Microvascular Resistance.

BACKGROUND: To validate a simplified invasive method for the calculation of the index of microvascular resistance (IMR). METHODS: This is a prospective, single-center study of patients with chronic coronary syndromes presenting with nonobstructive coronary artery disease. IMR was obtained using both intravenous (IV) adenosine and intracoronary (IC) papaverine. Each IMR measurement was obtained in duplicate. The primary objective was the agreement between IMR acquired using adenosine and papaverine. Secondary objectives include reproducibility of IMR and time required for the IMR measurement. RESULTS: One hundred and sixteen IMR measurements were performed in 29 patients. The mean age was 68.8 ± 7.24 years, and 27.6% was diabetics. IMR values were similar between papaverine and adenosine (17.7 ± 7.26 and 20.1 ± 8.6, p=0.25; Passing-Bablok coefficient A 0.58, 95% CI -2.42 to 3.53; coefficient B 0.90, 95% CI -0.74 to 1.07). The reproducibility of IMR was excellent with both adenosine and papaverine (ICC 0.78, 95% CI 0.63 to 0.88 and ICC 0.93, 95% CI 0.87 to 0.97). The time needed for microvascular assessment was significantly shortened by the use of IC papaverine (3.23 (2.84, 3.78) mins vs. 5.48 (4.94, 7.09) mins, p < 0.0001). CONCLUSION: IMR can be reliably measured using IC papaverine with similar results compared to intravenous infusion of adenosine with increased reproducibility and reduced procedural time. This approach simplifies the invasive assessment of the coronary microcirculation in the catheterization laboratory.

Basics of Coronary Thermodilution.

Coronary microvascular dysfunction is a highly prevalent condition in both obstructive and nonobstructive coronary artery disease. Intracoronary thermodilution is a promising technique to investigate coronary microvascular (dys)function in vivo and to assess its most important metric: microvascular resistance. Here, the authors provide a practical review of bolus and continuous thermodilution for the measurement of coronary flow and microvascular resistance. The authors describe the basic principles of indicator-dilution theory and of coronary thermodilution and detail the practicalities of their application in the catheterization laboratory. Finally, the authors discuss contemporary clinical applications of coronary thermodilution-based microvascular assessment in humans and future perspectives.

Thermodilution-derived volumetric resting coronary blood flow measurement in humans.

BACKGROUND: Quantification of microvascular function requires the measurement of flow and resistance at rest and during hyperaemia. Continuous intracoronary thermodilution accurately measures coronary flow during hyperaemia. AIMS: The aim of this study was to investigate whether continuous coronary thermodilution using lower infusion rates also enables volumetric coronary blood flow measurements (in mL/min) at rest. METHODS: In 59 patients (88 arteries), the ratio of distal to proximal coronary pressure (Pd/Pa), as well as absolute blood flow (in mL/min) by continuous thermodilution, was recorded using a pressure/temperature guidewire. Saline was infused at rates of 10 and 20 mL/min. In 27 arteries, Doppler average peak velocity (APV) was measured simultaneously. Pd/Pa, APV, thermodilution-derived coronary flow reserve (CFRthermo) and coronary flow velocity reserve (CFVR) were assessed. In 10 arteries, simultaneous recordings were obtained at saline infusion rates of 6, 8, 10 and 20 mL/min. RESULTS: Compared to baseline, saline infusion at 10 mL/min did not change Pd/Pa (0.95±0.05 versus 0.94±0.05, p=0.49) or APV (22±8 versus 23±8 cm/s, p=0.60); conversely, an infusion rate of 20 mL/min induced a decrease in Pd/Pa and an increase in APV. Stable thermodilution tracings were obtained during saline infusion at 8 and 10 mL/min, but not at 6 mL/min. Mean values of CFRthermo and CFVR were similar (2.78±0.91 versus 2.76±1.06, p=0.935) and their individual values correlated closely (r=0.89, 95% CI: 0.78-0.95, p<0.001). CONCLUSIONS: In addition to hyperaemic flow, continuous thermodilution can quantify absolute resting coronary blood flow; therefore, it can be used to calculate coronary flow reserve and microvascular resistance reserve.

Normal values of thermodilution-derived absolute coronary blood flow and microvascular resistance in humans.

BACKGROUND: Absolute hyperaemic coronary blood flow (Q, in mL/min) and resistance (R, in Wood units [WU]) can be measured invasively by continuous thermodilution. AIMS: The aim of this study was to assess normal reference values of Q and R. METHODS: In 177 arteries (69 patients: 25 controls, i.e., without identifiable coronary atherosclerosis; 44 patients with mild, non-obstructive atherosclerosis), thermodilution-derived hyperaemic Q and total, epicardial, and microvascular absolute resistances (Rtot, Repi, and Rmicro) were measured. In 20 controls and 29 patients, measurements were obtained in all three major coronary arteries, thus allowing calculations of Q and R for the whole heart. In 15 controls (41 vessels) and 25 patients (71 vessels), vessel-specific myocardial mass was derived from coronary computed tomography angiography. RESULTS: Whole heart hyperaemic Q tended to be higher in controls compared to patients (668±185 vs 582±138 mL/min, p=0.068). In the left anterior descending coronary artery (LAD), hyperaemic Q was significantly higher (293±102 mL/min versus 228±71 mL/min, p=0.004) in controls than in patients. This was driven mainly by a difference in Repi (43±23 vs 83±41 WU, p=0.048), without significant differences in Rmicro. After adjustment for vessel-specific myocardial mass, hyperaemic Q was similar in the three vascular territories (5.9±1.9, 4.9±1.7, and 5.3±2.1 mL/min/g, p=0.44, in the LAD, left circumflex and right coronary artery, respectively). CONCLUSIONS: The present report provides reference values of absolute coronary hyperaemic Q and R. Q was homogeneously distributed in the three major myocardial territories but the large ranges of observed hyperaemic values of flow and of microvascular resistance preclude their clinical use for inter-patient comparison.

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.

Vessel Fractional Flow Reserve and Graft Vasculopathy in Heart Transplant Recipients.

BACKGROUND: Cardiac allograft vasculopathy (CAV) remains the Achilles' heel of long-term survival after heart transplantation (HTx). The severity and extent of CAV is graded with conventional coronary angiography (COR) which has several limitations. Recently, vessel fractional flow reserve (vFFR) derived from COR has emerged as a diagnostic computational tool to quantify the functional severity of coronary artery disease. PURPOSE: The present study assessed the usefulness of vFFR to detect CAV in HTx recipients. METHODS: In HTx patients referred for annual check-up, undergoing surveillance COR, the extent of CAV was graded according to the criteria proposed by the international society of heart and lung transplantation (ISHLT). In addition, three-dimensional coronary geometries were constructed from COR to calculate pressure losses using vFFR. RESULTS: In 65 HTx patients with a mean age of 53.7 ± 10.1 years, 8.5 years (IQR 1.90, 15.2) years after HTx, a total number of 173 vessels (59 LAD, 61 LCX, and 53 RCA) were analyzed. The mean vFFR was 0.84 ± 0.15 and median was 0.88 (IQR 0.79, 0.94). A vFFR ≤ 0.80 was present in 24 patients (48 vessels). HTx patients with a history of ischemic cardiomyopathy (ICMP) had numerically lower vFFR as compared to those with non-ICMP (0.70 ± 0.22 vs. 0.79 ± 0.13, p = 0.06). The use of vFFR reclassified 31.9% of patients compared to the anatomical ISHLT criteria. Despite a CAV score of 0, a pathological vFFR ≤ 0.80 was detected in 8 patients (34.8%). CONCLUSION: The impairment in epicardial conductance assessed by vFFR in a subgroup of patients without CAV according to standard ISHLT criteria suggests the presence of a diffuse vasculopathy undetectable by conventional angiography. Therefore, we speculate that vFFR may be useful in risk stratification after HTx.

Clinical Outcomes Following Coronary Bifurcation PCI Techniques: A Systematic Review and Network Meta-Analysis Comprising 5,711 Patients.

OBJECTIVES: The aim of this study was to compare clinical outcomes of different bifurcation percutaneous coronary intervention (PCI) techniques. BACKGROUND: Despite several randomized trials, the optimal PCI technique for bifurcation lesions remains a matter of debate. Provisional stenting has been recommended as the default technique for most bifurcation lesions. Emerging data support double-kissing crush (DK-crush) as a 2-stent technique. METHODS: PubMed and Scopus were searched for randomized controlled trials comparing PCI bifurcation techniques for coronary bifurcation lesions. Outcomes of interest were major adverse cardiovascular events (MACE). Secondary outcomes of interest were cardiac death, myocardial infarction, target vessel or lesion revascularization, and stent thrombosis. Summary odds ratios (ORs) were estimated using Bayesian network meta-analysis. RESULTS: Twenty-one randomized controlled trials including 5,711 patients treated using 5 bifurcation PCI techniques were included. Investigated techniques were provisional stenting, T stenting/T and protrusion, crush, culotte, and DK-crush. Median follow-up duration was 12 months (interquartile range: 9 to 36 months). When all techniques were considered, patients treated using the DK-crush technique had less occurrence of MACE (OR: 0.39; 95% credible interval: 0.26 to 0.55) compared with those treated using provisional stenting, driven by a reduction in target lesion revascularization (OR: 0.36; 95% credible interval: 0.22 to 0.57). No differences were found in cardiac death, myocardial infarction, or stent thrombosis among analyzed PCI techniques. No differences in MACE were observed among provisional stenting, culotte, T stenting/T and protrusion, and crush. In non-left main bifurcations, DK-crush reduced MACE (OR: 0.42; 95% credible interval: 0.24 to 0.66). CONCLUSIONS: In this network meta-analysis, DK-crush was associated with fewer MACE, driven by lower rates of repeat revascularization, whereas no significant differences among techniques were observed for cardiac death, myocardial infarction, and stent thrombosis. A clinical benefit of 2-stent techniques was observed over provisional stenting in bifurcation with side branch lesion length ≥10 mm.

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.

Measurement of Hyperemic Pullback Pressure Gradients to Characterize Patterns of Coronary Atherosclerosis.

BACKGROUND: Diffuse atherosclerosis is commonly observed in angiographically normal segments in patients with stable coronary artery disease (CAD). The distribution of epicardial resistance along the vessel can be evaluated using coronary physiology. OBJECTIVES: The purpose of this study was to characterize the pathophysiological patterns of CAD using invasive pressure pullbacks during continuous hyperemia. METHODS: In this prospective, multicenter study of patients undergoing clinically-indicated coronary angiography due to stable angina, a pressure-wire pullback device was set at a speed of 1 mm/s. Based on coronary angiography and on the fractional flow reserve (FFR) pullback curve, the patterns of CAD were adjudicated as focal, diffuse, or a combination of both. The distribution of epicardial resistance was characterized using the hyperemic pullback pressure gradients (PPGs). The PPG index, a continuous metric based on the magnitude of pressure drop over 20 mm and on the extent of functional disease was computed to determine the pattern of CAD. Low PPG index indicates diffuse CAD. RESULTS: A total of 158 vessels (n = 117) were included. Overall, 984,813 FFR values were used to generate 100 FFR pullback curves. Using coronary physiology, 36% of the vessel disease patterns were reclassified compared to angiography. The median of maximal PPG over 20 mm was 0.083 (interquartile range: 0.063 to 0.118) FFR units, and the mean extent of functional disease was 39.3 ± 21.3 mm. The mean PPG index was 0.58 ± 0.18 and differentiated pathophysiological focal and diffuse disease (p < 0.001). CONCLUSIONS: Pathophysiological patterns of CAD can be characterized by motorized hyperemic PPGs. The evaluation of the FFR pullback curve reclassified one-third of the vessels' disease patterns compared with conventional angiography. The PPG index is a novel metric that quantifies the distribution of epicardial resistance and discriminates focal from diffuse CAD. (Physiological Patterns of Coronary Artery Disease; NCT03824600).