Multivessel Coronary Function Testing Increases Diagnostic Yield in Patients With Angina and Nonobstructive Coronary Arteries

BACKGROUND Invasive CFT is the gold standard for diagnosing coronary vasomotor dysfunction in patients with ANOCA. Most institutions recommend only testing the left coronary circulation. Therefore, it is unknown whether testing multiple coronary territories would increase diagnostic yield. OBJECTIVES The aim of this study was to evaluate the diagnostic yield of multivessel, compared with single-vessel, invasive coronary function testing (CFT) in patients with angina and nonobstructive coronary arteries (ANOCA). METHODS Multivessel CFT was systematically performed in patients with suspected ANOCA. Vasoreactivity testing was performed using acetylcholine provocation in the left (20 to 200 m g) and right (20 to 80 m g) coronary arteries. A pressure-temperature sensor guidewire was used for coronary physiology assessment in all three epicardial vessels. RESULTS This multicenter study included a total of 228 vessels from 80 patients (57.8 (cid:1) 11.8 years of age, 60% women). Compared with single-vessel CFT, multivessel testing resulted in more patients diagnosed with coronary vasomotor dysfunction (86.3% vs 68.8%; P ¼ 0.0005), coronary artery spasm (60.0% vs 47.5%; P ¼ 0.004), and CMD (62.5% vs 36.3%; P < 0.001). Coronary artery spasm (n ¼ 48) predominated in the left coronary system (n ¼ 38), though isolated right coronary spasm was noted in 20.8% (n ¼ 10). Coronary microvascular dysfunction (CMD), de ﬁ ned by abnormal index of microcirculatory resistance and/or coronary ﬂ ow reserve, was present 62.

N early one-half of all patients who undergo coronary angiography for stable angina are found to have nonobstructive coronary arteries (ANOCA). 1 Coronary vasomotor dysfunction (CVDys), including coronary (epicardial and microvascular) artery spasm (CAS) and/or coronary microvascular dysfunction (CMD), is the underlying pathophysiology in 60% to 90% of these patients. 2,3CVDys is characterized by a relative mismatch between coronary artery blood flow and oxygen demand, resulting in angina pectoris and myocardial ischemia.It is associated with high rates of morbidity, including an impaired quality of life and recurrent hospitalizations, resulting in significant utilization of health care resources. 1,4,5vasive coronary angiography (ICA) remains the gold standard for the diagnosis of obstructive coronary artery disease (CAD), but its diagnostic utility is limited in cases of ANOCA.Invasive coronary function testing (CFT), using acetylcholine (ACH) to diagnose coronary (epicardial and microvascular) spasm and adenosine to evaluate the structural and functional integrity of the microcirculation, is considered the gold standard for evaluating patients with ANOCA.The European Society of Cardiology and American College of Cardiology/American Heart Association guidelines advocate using CFT to characterize ANOCA patients into distinct endotypes. 6,7This classification allows clinicians to tailor therapy to individual patients, an approach that has shown to improve angina status and quality of life. 8T is typically performed on a single coronary vessel.Testing the left coronary circulation, specifically the left anterior descending artery (LAD), is recommended as it typically subtends the largest myocardial territory. 9In cases where technical factors, such as tortuous coronary anatomy, preclude instrumentation of the LAD, testing of the left circumflex coronary artery (LCx) and right coronary artery (RCA) may be considered. 9Although singlevessel testing assumes that disorders of coronary vasomotion are pan-coronary, previous studies suggest the existence of regional discrepancies across different coronary territories. 10Current practice is based on consensus, and it is unclear whether testing multiple coronary territories would increase diagnostic yield.The purpose of this study was to evaluate the diagnostic efficacy of multivessel CFT in patients with ANOCA.

METHODS
This multicenter, prospective observational study assessed multivessel CFT in patients with ANOCA.All patients were referred by their treating cardiologist for suspected CVDys.Diagnostic ICA was performed to confirm the absence of obstructive CAD, defined as a visual stenosis of more than 50% in combination with a measured resting full-cycle ratio #0.89 and/or fractional flow reserve (FFR) #0.80. 11Patients ($18 years) underwent ACH provocation followed by adenosine-mediated coronary physiology assessment in all 3 major epicardial arteries (Supplemental Figure 1).There was a minimum interval of 10 minutes between both procedures.In the case of a small, nondominant, or severely tortuous coronary with a 2-minute gap between doses.After each injection, cine-images were obtained to assess the change in coronary diameter through quantitative coronary angiography, as previously described. 14If CAS was induced with reproducible symptoms and ST-segment changes (see definitions in the following text), the provocation test was terminated and concluded to be positive.For the RCA, a similar protocol was followed with incremental doses of 20, 50, and 80 mg of ACH.When coronary spasm was induced and did not resolve spontaneously within 3 minutes following the completion of ACH testing, or in instances of hemodynamic instability, nitroglycerin was administrated.
Coronary physiology assessment was completed using a pressure-temperature sensor guidewire (PressureWire X, Abbott).After equalizing to guide catheter pressure, the guidewire was advanced ensuring the sensor position was in the distal third of the vessel and at least 80 mm from the guiding catheter.If not already done, intracoronary nitroglycerin was administered at a dose of 200 mg.The resting mean proximal (Pa) and distal pressure (Pd) was recorded.Three boluses of 3 mL of room temperature saline were injected into the coronary artery via the guiding catheter.The transit time of the saline injections was determined using the thermodilution technique, and the average of the 3 resting transit times was recorded as the resting mean transit time (TmnR).Next, an intravenous infusion of adenosine (140 mg/kg/min) was administered via a large-bore peripheral cannula or femoral venous sheath to induce a steady state of maximal hyperemia.The hyperemic mean proximal pressure and distal pressure were recorded.Thermodilution curves were then produced in the same manner to determine the hyperemic mean transit time (TmnH).The calculations for the respective coronary hemodynamic indices include: 1) Pd/Pa during hyperemia for FFR; 2) TmnR/TmnH for coronary flow reserve (CFR); and 3) Pd Â TmnH for index of microcirculatory resistance (IMR).All measurements were recorded using the CoroFlow system (Coroventis Research).
DEFINITIONS.CVDys was defined according to the underlying pathophysiological endotype as per previously published international consensus. 15,16icardial spasm was defined as a focal or diffuse epicardial coronary diameter reduction >90% in response to ACH compared with the relaxed state after intracoronary nitroglycerin, with a reproduction of recognizable symptoms and ischemic ECG changes.
Microvascular spasm was diagnosed when there was a reproduction of recognizable symptoms with ischemic ECG changes in the absence of >90% Assuming a 50% diagnostic rate using conventional single-vessel CFT in patients with ANOCA, a sample size of 78 patients was calculated to achieve 80% statistical power for detecting a 10% difference in diagnosis.The significance level was set at 5%.All analyses were performed using R version 4.2.2.
(R Foundation for Statistical Computing). 17

RESULTS
This study was conducted across 2 tertiary referral institutions, including 228 vessels from 80 patients.
The patient cohort had a mean age of 57.8 AE 11.8 years, with 60% of the participants being women.Clinical and medication data are presented in Table 1.Patients with CVDys were more likely to receive beta-blocker therapy (45.5% vs 14.3%; P ¼ 0.03).In addition, there was a trend among this group toward being overweight (66.6% vs 35.7%;P ¼ 0.074).
Rest angina was reported in 25%, exertional angina in 35%, and mixed rest and exertional angina in the remaining 40%.
ANGINA AND QUALITY OF LIFE MEASURES.
Among    demonstrated that spasm in the LCx (28.3%) was significantly less frequent (P < 0.001) than that in the RCA (73.3%) and LAD (72%). 22These observations were subsequently validated in other studies, suggesting that the LCx may be less responsive to ACH provocation due to its smaller myocardial territory. 23,24These results mirrored the present study, where spasm in the LCx was observed in only 31.3% (15/48) of patients.
Notably, some studies have avoided provocative testing in the RCA to reduce procedural time and contrast administration. 2,23,25,26Such an approach may compromise diagnostic yield and overlook the presence of multivessel spasm, a well-known poor prognostic indicator. 27,28In the current study,    Their findings were consistent with the present study, which observed a similar prevalence of CMD in territories supplied by all 3 major coronary vessels (LAD ¼ 36.3%,LCx ¼ 33.8%, RCA ¼ 31.3%;P ¼ 0.486).
Notably, the incidence of abnormal CFR, a wellestablished prognostic marker in this population, exhibited no significant differences among the three vessels.
Unlike our present study, Kobayashi et al 31 did not include comprehensive CFT, specifically the inclusion of ACH testing.Nevertheless, our collective findings suggest that abnormalities of the coronary microcirculation may be regional, and conventional CMD testing in a single coronary territory may be limited in its ability to detect abnormalities.This raises important questions about the validity of current methods for assessing CMD and suggest that multivessel testing may be a more effective approach to identifying abnormalities in the coronary microcirculation.7][38][39][40] The latter typically entails angiotensin-  Abbreviations as in Figures 1 and 2.
abnormalities, such as enhanced coronary vasoreactivity and elevated microvascular resistance, which are associated with a worse prognosis. 3Interestingly, when evaluating symptoms using the SAQ, no difference in angina burden was observed for patients with CVDys isolated to a non-LAD vessel.
Notably, the presence of multivessel CMD was associated with a lower angina-related quality of life.This highlights the importance of multivessel CFT in refining the diagnostic process and potentially improving patient outcomes through a more personalized approach to treatment.
CLINICAL RECOMMENDATION.Drawing from our experience and critical evaluation of prior studies, we advocate for multivessel CFT in patients with ANOCA (Figure 4).We recommended initiating testing in the LAD unless there is a strong clinical suspicion for   ANOCA testing centers by their treating physicians, which may have influenced the high yield of abnormalities observed.Nevertheless, the prevalence of abnormalities observed in this study was consistent with that reported in previous literature.We did not specifically test for endothelial dysfunction using a low-dose, slow ACH infusion, potentially impacting the diagnostic yield of CFT.Given ease of use, availability, and clinician expertise, thermodilution method was used in coronary physiology assessment though we acknowledge that Doppler flow velocity or absolute flow measurements may provide a more accurate assessment.
artery, CFT was avoided for safety reasons.Patients demonstrating resting or hyperemic indices indicative of obstructive CAD were subsequently excluded from the study.In addition, patients were excluded if there was a noncoronary indication for invasive angiography (eg, valve disease), technical factors precluding safe passage of the pressure guidewire, an inability to receive adenosine, a recent (within 3 weeks before cardiac catheterization) ST-segment elevation myocardial infarction, and/or an inability to provide informed consent.Clinical data of patient characteristics, cardiac risk factors, and symptom profile were acquired before CFT.Information on traditional cardiovascular risk factors (eg, diabetes, hypercholesterolemia, hypertension, premature CAD in first-degree relatives) and nontraditional variables associated with vasomotor dysfunction (eg, caffeine intake) 12,13 were noted.In addition, patients were asked to report angina characteristics and quality of life measures through the Seattle Angina Questionnaire (SAQ).The study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki and was approved by the human research ethics review board.Written informed consent was obtained from all participants.INVASIVE CFT.All CFT was performed in the morning, and patients were requested to withhold vasoactive medications (eg, calcium channel blockers, long-acting nitrates, beta-blockers) and methylxanthine-containing substances for 24 to 72 hours, depending on the drug half-life.Throughout the procedure, a continuous 12-lead electrocardiogram (ECG) was monitored, while standard resuscitation equipment was made available.ICA was performed per standard institutional practice via the radial or femoral route.Administration of A B B R E V I A T I O N S A N D A C R O N Y M S ACH = acetylcholine ANOCA = angina and nonobstructive coronary arteries CAD = coronary artery disease CAS = coronary artery spasm CFR = coronary flow reserve CFT = coronary function testing CMD = coronary microvascular dysfunction CVDys = coronary vasomotor dysfunction ECG = electrocardiogram FFR = fractional flow reserve ICA = invasive coronary angiography IMR = index of microcirculatory resistance LAD = left anterior descending coronary artery LCA = left coronary artery LCx = left circumflex coronary artery RCA = right coronary artery SAQ = Seattle Angina Questionnaire TPW = temporary pacing wire intra-arterial vasodilator drugs (eg, nitroglycerin, calcium channel blockers) was avoided before CFT in all patients.A standard diagnostic ICA was performed to confirm the absence of obstructive CAD.If no obstructive CAD was present, we proceeded to perform CFT.The choice of first vessel to be tested was left to the operator's discretion.We then proceeded to perform CFT on the remaining major epicardial coronary arteries.Coronary vasoreactivity was assessed via ACH provocation.To compensate for potential bradycardia, a temporary pacing wire (TPW) was inserted via the femoral vein.Activation of the TPW was contingent upon a pause exceeding 5 seconds.A 6-F angioplasty guiding catheter without side holes was inserted into either the left coronary artery (LCA) or RCA, per the operator's clinical judgment.For the LCA assessment, incremental doses of 20, 50, 100, and 200 mg of ACH were injected over 20 seconds, epicardial diameter reduction in response to ACH.Ischemic ECG changes were defined as transient ST-segment elevation or depression of >0.1 mV, or ischemic T-wave changes, in at least 2 contiguous leads.CMD was confirmed if coronary physiology assessment demonstrated a CFR <2.5 and/or IMR $25, as defined by current consensus documents. 6A diagnosis of noncardiac chest pain required no obstructive epicardial CAD (FFR >0.80) and normal CFT (CFR $2.5, IMR <25, and negative ACH testing).STATISTICAL ANALYSIS.Continuous data are presented as mean AE SD or median (Q1-Q3), as appropriate.Categorical data are presented as count (%).The chi-square or Fisher exact test was used as appropriate for categorical data analysis.McNemar's test was used to assess the change in diagnostic yield of multivessel compared with single-vessel CFT.P < 0.05 was considered statistically significant.

FIGURE 1
FIGURE 1 Efficacy of Multivessel CFT in Reclassifying ANOCA Endotypes of patients undergoing multivessel testing in a similar population cohort.Interestingly, other studies present a diverse prevalence of CAS, ranging from 59% to 71%.[19][20][21]This variability can be attributed to the heterogeneity in current diagnostic protocols, including differences in administration time, dosage regimen, and the specific vessels assessed.Previous research by Sueda and Kohno 22 explored the distribution of CAS within specific coronary arteries in a retrospective analysis of 1,392 patients.Results 10 patients (20.8%) were found to have isolated RCA spasm, emphasizing the significance of comprehensive multivessel testing.As suggested by Feenstra et al, 29 the omission of RCA testing could result in overlooked diagnoses, significantly impacting the clinical management and prognosis of these patients.DIAGNOSTIC IMPACT OF MULTIVESSEL CFT IN CMD.Multivessel CFT provides greater insight into abnormalities of the coronary microcirculation.The present study revealed almost two-thirds (62.5%) of participants who underwent multivessel coronary physiology testing demonstrated an abnormal response.By contrast, only 36.3% who underwent single-vessel

FIGURE 2
FIGURE 2 Prevalence of CAS and CMD testing exhibited abnormalities.These results align with earlier research that reported prevalence rates ranging from 29% to 44% in single-vessel testing of the coronary microvasculature. 2,3,8,30Notably, Kobayashi et al 31 conducted a prospective study utilizing multivessel coronary physiology testing to identify clinical and angiographic predictors of an abnormal IMR.The study revealed that only 68% of patients with CMD were diagnosed in the LAD territory, highlighting that a considerable proportion (32%) were missed through single-vessel testing. 31 CLINICAL RELEVANCE MULTIVESSEL CFT INANOCA.ANOCA represents a complex clinical entity that frequently poses diagnostic challenges to clinicians.These individuals experience a decreased quality of life, are subject to repeated coronary angiograms, and have an elevated risk of adverse events.1,32Precise identification of ANOCA endotypes is crucial for determining the most appropriate pharmacological therapy for such patients.Calcium channel blockers are the first-line drug of choice for patients with epicardial or microvascular spasm.33 converting enzyme inhibitors or angiotensin receptor blockers and statins, which may enhance endothelial function and improve hyperemic myocardial blood flow. 41Multivessel CFT can significantly increase the proportion of patients diagnosed with CVDys and even alter the initially diagnosed ANOCA endotype, necessitating re-evaluation of the treatment approach.This is crucial, as distinct pathophysiological mechanisms may exist, and current diagnostic methods can misclassify patients.This has implications for the treatment of current patients and poses challenges for future therapeutic clinical trials, where inaccurate identification of ANOCA endotypes can confound results.Moreover, multivessel CFT can uncover coexisting coronary functional

FIGURE 3
FIGURE 3 Prevalence of ANOCA Endotypes as Determined by Single and Multivessel CFT regional CMD or spasm.Should uncertainty persist after ACH provocation and/or coronary physiology assessment, we recommend testing the contralateral epicardial artery (LCx and/or RCA).This pragmatic approach facilitates precise identification of the underlying ANOCA endotype, thereby influencing clinical management.During CFT, ACH testing can be performed either before or after coronary physiology assessment as the optimal sequence is still under debate.Although multivessel CFT offers comprehensive diagnostic insights, examining the potential downsides associated with this approach is essential.Compared with single-vessel, multivessel testing had a longer median procedural time (56 minutes [Q1-Q3: 48-62 minutes] vs 40.5 minutes [Q1-Q3: 35.5-46 minutes]) and increased contrast administration (155 mL [Q1-Q3: 135-180 mL] vs 110 mL [Q1-Q3: 90-120 mL]).Additionally, 1 serious adverse event occurred.Careful patient selection and operator expertise are essential in minimizing the potential risks with multivessel CFT.STUDY LIMITATIONS.Limitations of the present study are inherent to the internationally recognized protocols and diagnostic criteria for chronic coronary syndromes.The study population comprised a selectively chosen group of patients referred to expert

FIGURE 4
FIGURE 4 Invasive Diagnostic Algorithm for Multivessel CFT .

Table 2 .
the 42 patients with epicardial spasm, a diffuse pattern was observed in 24 patients (57.1%), whereas
Dr Rehan is supported by the National Health and Medical Research Council Postgraduate Scholarship.Dr Chan has received research support from Abbott Vascular.Dr Tremmel has received honoraria from Boston Scientific, Abbott Vascular, and Shockwave.Dr Fearon has received research support from Abbott Vascular and Medtronic; and has minor stock options with HeartFlow.Dr Ng has received research support from Abbott Vascular.Dr Yong has received minor honoraria and research support from Abbott Vascular, Boston Scientific and Philips Healthcare.All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.ADDRESS FOR CORRESPONDENCE: Dr Andy S.C. Yong, Department of Cardiology, Concord Repatriation General Hospital, Hospital Road, Concord, NSW 2137, Australia.E-mail: andy.yong@sydney.edu.au.Demir Ozan M, Boerhout Coen KM, de Waard Guus A, et al.Comparison of Doppler flow velocity and thermodilution derived indexes of coronary physiology.J Am Coll Cardiol Intv.2022;15:1060-1070.https://doi.org/10.1016/j.jcin.2022.03.015 43.Everaars H, de Waard GA, Driessen RS, et al.Doppler flow velocity and thermodilution to assess coronary flow reserve: a head-to-head comparison with [(15)O]H(2)O PET.J Am Coll Cardiol Intv.2018;11:2044-2054.https://doi.org/10.1016/j.jcin.2018.07.011 44.Seitz A, Feenstra R, Konst RE, et al.Acetylcholine rechallenge: a first step toward tailored treatment in patients with coronary artery spasm.J Am Coll Cardiol Intv.2022;15: 65-75.https://doi.org/10.1016/j.jcin.2021.10.003 KEY WORDS ANOCA, coronary artery spasm, coronary microvascular dysfunction, coronary vasomotor dysfunction, multivessel coronary function testing APPENDIX For supplemental figures and tables, please see the online version of this paper. 42.