Carrington, Justin

Background: Coronary microvascular dysfunction (CMD) is a common cause of angina with non-obstructive coronary arteries (ANOCA), but its role in patients with a history of myocardial infarction with non-obstructive coronary arteries (MINOCA) is much less understood. We investigated the incidence of major adverse cardiac and cerebrovascular events (MACCE) in patients undergoing invasive assessment for CMD, divided into patients with MINOCA versus patients with ANOCA. We hypothesized that CMD would be common in both groups. Methods: Serial patients undergoing invasive coronary provocation testing between 2012 and 2022 were divided into MINOCA (n=76) or ANOCA (n=561). Doppler study was performed in the left anterior descending artery. CMD was defined as either coronary flow reserve (CFR) <2.5 with adenosine or <50% increase in flow with acetylcholine. Patients were followed prospectively through 2025. Incidence of MACCE (cardiac death, non-fatal MI, hospitalization for heart failure, urgent revascularization, and stroke) was compared between MINOCA and ANOCA and further analyzed by CMD status. Kaplan-Meier curves were constructed and Cox proportional hazards models were used to estimate hazard ratios (HRs). Results: Among patients with MINOCA, 53 of 76 (70%) had CMD, compared to 363 of 561 (65%) with ANOCA. Invasive provocation testing was performed a median of 163 days (IQR 13 – 255 days) after the MI in the MINOCA group. Patients were then followed for a median of 4.4 years (IQR 3.0 – 6.9 years). MACCE-free survival was significantly lower in patients with MINOCA compared to those with ANOCA (HR = 3.57, p < 0.001; Figure 1). The major contributor to MACCE was non-fatal MI in MINOCA (24%) and heart failure hospitalization in ANOCA (6%). The presence of CMD was associated with worse prognosis in both MINOCA (HR = 3.76, p = 0.02) and ANOCA (HR = 8.35, p < 0.001; Figure 2). Conclusions: Patients with MINOCA experience significantly higher long-term risk of major adverse events compared to those with ANOCA. CMD is common in both groups and is independently associated with worse outcomes. Specifically, patients with CMD had higher rates of MACCE over time, regardless of whether they presented with MINOCA or ANOCA. Invasive assessment of CMD in patients with myocardial infarction and non-obstructive coronary arteries may improve risk stratification and inform management strategies in these understudied populations

Background: Coronary microvascular disease (CMD) may be endothelium-independent (coronary flow reserve, CFR < 2.5) or endothelium-dependent (<50% increase in coronary blood flow in response to acetylcholine). CMD has been implicated in abnormal myocardial relaxation and impaired diastolic function. Wave intensity analysis (WIA) is a hemodynamic method that quantifies the energy of pressure-flow waves driving coronary blood flow. The backward expansion wave (BEW) is the dominant distally originating wave, generated by microvascular suction during ventricular relaxation. Thus, the BEW may offer mechanistic insight into the link between CMD and diastolic dysfunction. Hypothesis: We hypothesized that diastolic dysfunction would be more common in patients with CMD, and that the backward expansion wave (BEW) intensity would be lower in those with diastolic dysfunction compared to those without. Methods: Patients with non-obstructive coronary artery disease undergoing invasive coronary physiology assessment of the left anterior descending artery were included (n = 113). Pressure and Doppler flow were recorded at rest, with adenosine, and with acetylcholine for categorization of CMD as endothelium-independent (CMD-Ei) and/or endothelium-dependent (CMD-Ed). Wave intensity analysis was used to calculate cumulative BEW (J×m -2 ) at rest in CMD, CMD-Ei (endothelium-independent), and CMD-Ed (endothelium-dependent) subgroups. Diastolic dysfunction was diagnosed by transthoracic echocardiogram using the 2016 American Society of Echocardiography (ASE) guidelines. Results: Of the 113 study patients, 88 (77.9%) had CMD and 25 (22.1%) did not. Among those with CMD, 39 patients (44.3%) had diastolic dysfunction (Figure 1). In the patients with CMD, the BEW intensity was significantly lower in patients with diastolic dysfunction compared to those without (6.5 vs. 9.0 × 10 3 W×m -2 ×s -1 , p < 0.05). The same trend was observed for the CMD-Ei (7.2 vs. 9.7 × 10 3 W×m -2 ×s -1 , p < 0.05) and CMD-Ed (6.2 vs. 9.1 × 10 3 W×m -2 ×s -1 , p < 0.05) subtypes. Conclusions: Diastolic dysfunction is frequent in patients with invasively diagnosed CMD. Patients with CMD who have diastolic dysfunction have comparatively lower BEW intensity, regardless of endothelial subtype. Since the BEW is the major driver of coronary flow during diastole, this suggests a mechanism by which CMD may lead to diastolic dysfunction.

Background: Coronary wave intensity analysis (WIA) provides a mechanistic view of coronary hemodynamics and has been increasingly used to phenotype coronary microvascular disease (CMD). Standard WIA requires simultaneous pressure and flow measurements within the same vessel, but intra-coronary pressure measurement may be limited by hardware availability. In patients with non-obstructive coronary arteries, aortic pressure may serve as a surrogate for intra-coronary pressure to enable broader feasibility of WIA. We aimed to determine whether wave profiles derived from intra-aortic and intra-coronary pressure measurements are comparable when paired with intracoronary Doppler flow in patients with non-obstructive coronary artery disease. Methods: Patients undergoing invasive coronary physiology assessment of the left anterior descending artery were included. Intracoronary flow velocity and intra-coronary pressure were simultaneously recorded using a ComboWire (Philips Volcano) in the proximal LAD. Aortic pressure was concurrently measured via the guide catheter to allow comparison of pressure sources. In the intra-aortic pressure group, pressure and flow data were aligned using the R wave of the ECG trace. WIA was performed using conventional methods to quantify the dominant waves: forward compression wave (FCW), backward compression wave (BCW), and backward expansion wave (BEW). Agreement between wave intensity was assessed using Bland-Altman analysis and Pearson correlation. Results: A total of 14 paired waveforms were analyzed with a total of 42 coronary waves compared. Wave intensities calculated using intra-coronary versus intra-aortic pressure showed excellent agreement across all wave types. Mean bias between methods was −0.07 x 10 3 W×m -2 ×s -1 with limits of agreement from −0.63 to +0.49. The correlation between intra-coronary and intra-aortic wave intensities was strong (r = 0.997, p < 0.001), with minimal dispersion and consistent agreement across the full range of wave intensities ( Figure 1 ). Conclusions: In patients with non-obstructive coronary arteries, wave intensity analysis using guide-catheter aortic pressure yields results nearly identical to those obtained with intra-coronary pressure. These findings support the use of aortic pressure as a reliable surrogate for intra-coronary pressure in WIA for the calculation of microvascular coronary hemodynamics, reducing technical barriers and enabling broader clinical and research utilization.

Background: Coronary microvascular disease (CMD) may be endothelium-independent (coronary flow reserve, CFR<2.5) or endothelium-dependent (<50% increase in coronary blood flow in response to acetylcholine). Endothelium-independent CMD has been subclassified into structural and functional groups based on hyperemic microvascular resistance (hMR, mmHg/cm/s). We hypothesized that endothelium-dependent CMD also has these subtypes. Methods: Patients with non-obstructive coronary artery disease who underwent coronary catheterization of the left anterior descending artery were included (n=112). Pressure and flow were recorded at rest, with adenosine, and with acetylcholine. Patients were classified by endothelial type and functional CMD (hMR<2.5) or structural CMD (hMR>2.5). Wave intensity analysis was performed and cumulative separated wave intensity (Joules/m 2 ) was calculated by standard formulae. Three dominant waves were analyzed (forward compression wave, FCW; backward compression wave, BCW; backward expansion wave, BEW). Results: Seventy-four of 109 patients had CMD, of which 59 had endothelium-independent and 38 had endothelium-dependent CMD (23 had both). Functional and structural subgroups were identified (Figure 1). All CMD subtypes had significantly different wave intensities at rest, adenosine, and acetylcholine (p<0.05). Comparing subtypes, there was no difference in wave intensities at rest. However, wave intensities significantly differed between all CMD subtypes with adenosine and acetylcholine, with higher energy waves in the endothelium-independent and functional groups (p<0.05, Figure 2). Conclusions: CMD is a heterogenous condition with distinct subtypes. Functional and structural groups exist in both endothelium-dependent and endothelium-independent CMD. These subgroups have distinct hemodynamic profiles as measured by wave intensity. A patient-specific approach to first line medical therapy may be improved by subgroup classification.

Abstract Background Six percent of patients presenting with acute myocardial infarction (MI) have MI with non-obstructed coronary artery disease (MINOCA). Coronary microvascular disease (CMD) is common in angina with non-obstructive coronary artery disease (ANOCA), but its prevalence and severity in MINOCA is undefined. Purpose Patients with CMD may have elevated risk of myocardial infarction despite no significant stenosis. We tested the hypothesis that patients with MINOCA have more significant burden of CMD than patients with ANOCA. Methods A retrospective case-control study was performed on patients who underwent invasive testing for signs of coronary ischemia and found to have non-obstructive disease (stenoses&lt; 50%). Cases of MI were classified as MINOCA (n=87) and compared to patients with ANOCA (n=552). Patients with spontaneous coronary artery dissection, myocarditis, Takotsubo cardiomyopathy or prior atherothrombotic MI were excluded. Coronary catheterization was performed followed by invasive provocation testing with adenosine and acetylcholine using a Doppler flow wire. CMD was subdivided into endothelium-independent, defined as coronary flow reserve (CFR) &lt; 2.5 with intra-coronary adenosine, and endothelium dependent, defined as &lt; 50% increase in coronary blood flow with acetylcholine. Epicardial vasoconstriction &gt; 90% with typical anginal symptoms was classified as epicardial vasospasm. Results There was no difference in age, sex or traditional coronary risk factors between the MINOCA and ANOCA groups (Table 1). Fifty (57%) of patients with MINOCA had type 2 MI secondary to supply-demand mismatch. Both MINOCA and suspected ANOCA patients had a high prevalence of CMD (71% vs 67%) and endothelium-independent CMD is more prevalent in MINOCA (64.5% vs 50.4%). Although odds of endothelium-dependent CMD were similar, the CFR within this group and CMD overall was worse in MINOCA patients (Figure 1). There was no difference in epicardial spasm. Conclusion Coronary microvascular disease and vasomotor dysfunction are common in patients with MINOCA, with a higher prevalence of endothelium-independent CMD and more severe CMD overall compared to patients with ANOCA. Treatment of CMD in patients with MINOCA may help reduce recurrence and warrants further investigation.