The Influence Of Epicardial Resistance On Microvascular Resistance Reserve

BACKGROUND

The optimal index of microvascular function should be specific for the microvascular compartment. Yet, coronary flow reserve (CFR), despite being widely used to diagnose coronary microvascular dysfunction (CMD), is influenced by both epicardial and microvascular resistance. Conversely, microvascular resistance reserve (MRR) adjusts for fractional flow reserve (FFR), and thus is theoretically independent of epicardial resistance.

OBJECTIVES

We tested the hypothesis that MRR, unlike CFR, is not influenced by increasing epicardial resistance, and thus is a more specific index of microvascular function.

METHODS

In a cohort of 16 patients that had undergone proximal left anterior descending artery stenting, we created four grades of artificial stenosis (no stenosis, mild, moderate, and severe) using a coronary angioplasty balloon inflated to different degrees within the stent. For each stenosis grade, we calculated CFR and MRR using continuous thermodilution (64 measurements of each) in order to assess their response to changing epicardial resistance.

RESULTS

Graded balloon inflation resulted in a significant sequential decrease in mean FFR (no stenosis: 0.82 ±0.05; mild: 0.72 ±0.04; moderate: 0.61 ±0.05; severe: 0.48 ±0.09, p<0.001). This translated into a linear decrease in mean hyperaemic coronary flow (no stenosis: 170.5 ±66.8 ml/min; mild: 149.8 ±58.8 ml/min; moderate: 124.4 ±53.0 ml/min; severe: 94.0 ±45.2 ml/min, p<0.001). CFR exhibited a marked linear decrease with increasing stenosis (no stenosis: 2.5 ±0.9; mild: 2.2 ±0.8; moderate: 1.8 ±0.7; severe: 1.4 ±0.6), corresponding to a decrease of 0.3 for a decrease in FFR of 0.1 (p<0.001). In contrast, MRR exhibited a negligible decrease across all stenosis grades (no stenosis: 3.0 ±1.0; mild: 3.0 ±1.0; moderate: 2.9 ±1.0; severe: 2.8 ±1.0), corresponding to a decrease of just 0.05 for a decrease in FFR of 0.1 (p<0.001).

CONCLUSION

MRR, unlike CFR, is minimally influenced by epicardial resistance, and thus should be considered the more specific index of microvascular function. This suggests that MRR can also reliably evaluate microvascular function in patients with significant epicardial disease.

Detection of transthyretin amyloid cardiomyopathy by automated data extraction from electronic health records

AIMS

Transthyretin amyloid cardiomyopathy (ATTR-CM), a progressive and fatal cardiomyopathy, is frequently misdiagnosed or entails diagnostic delays, hindering patients from timely treatment. This study aimed to generate a systematic framework based on data from electronic health records (EHRs) to assess patients with ATTR-CM in a real-world population of heart failure (HF) patients. Predictive factors or combinations of predictive factors related to ATTR-CM in a European population were also assessed.

METHODS AND RESULTS

Retrospective unstructured and semi-structured data from EHRs of patients from OLV Hospital Aalst, Belgium (2012-20), were processed using natural language processing (NLP) to generate an Observational Medical Outcomes Partnership Common Data Model database. NLP model performance was assessed on a random subset of EHRs by comparing algorithm outputs to a physician-generated standard (using precision, recall, and their harmonic mean, or F1-score). Of the 3127 HF patients, 103 potentially had ATTR-CM (age 78 ± 9 years; male 55%; ejection fraction of 48% ± 16). The mean diagnostic delay between HF and ATTR-CM diagnosis was 1.8 years. Besides HF and cardiomyopathy-related phenotypes, the strongest cardiac predictor was atrial fibrillation (AF; 72% in ATTR-CM vs. 60% in non-ATTR-CM, P = 0.02), whereas the strongest non-cardiac predictor was carpal tunnel syndrome (21% in ATTR-CM vs. 3% in non-ATTR-CM, P < 0.001). The strongest combination predictor was AF, joint disorders, and HF with preserved ejection fraction (29% in ATTR-CM vs. 18% in non-ATTR-CM: odds ratio = 2.03, 95% confidence interval = 1.28-3.22).

CONCLUSIONS

Not only well-known variables associated with ATTR-CM but also unique combinations of cardiac and non-cardiac phenotypes are able to predict ATTR-CM in a real-world HF population, aiding in early identification of ATTR-CM patients.

Assessment of E/A ratio helps emergency clinicians in the management of patients with acute dyspnea

Acute dyspnea (AD) is one of the main reasons for admission to the Emergency Department (ED). In the last years integrated ultrasound examination (IUE) of lung, heart and inferior vena cava (IVC) has become an extension of clinical examination for a fast differential diagnosis. The aim of present study is to assess the feasibility and diagnostic accuracy of E/A ratio for diagnosing acute heart failure (aHF) in patients with acute dyspnea. We included 92 patients presenting to the ED of CTO Hospital in Naples (Italy) for AD. All patients underwent IUE of lung-heart-IVC with a portable ultrasound device. Left ventricle diastolic function was assessed using pulse wave doppler at the tips of the mitral valve and E wave velocity and E/A ratio were recorded. The FINAL diagnosis was determined by two expert reviewers: acute HF or non-acute HF (non-aHF). We used 2 × 2 contingency tables to analyze sensitivity, specificity, positive predictive and negative predictive value of ultrasound parameters for the diagnosis of AD, comparing with the FINAL diagnosis. Lung ultrasound (LUS) showed high sensitivity, good specificity and accuracy in identification of patients with aHF. However, the highest accuracy was obtained by diastolic function parameters. The E/A ratio showed the highest diagnostic performance with an AUC for aHF of 0.93. In patients presenting with AD, E/A ratio is easy to obtain in a fast ultrasound protocol and showed an excellent accuracy for diagnosis of aHF.

268 IMPACT OF AORTIC REGURGITATION ON LONG TERM OUTCOME IN HEART FAILURE AND PRESERVED EJECTION FRACTION

Background

Aortic Regurgitation (AR) may aggravate the clinical course in patients with heart failure and preserved ejection fraction (HFpEF) by increasing filling pressures and triggering LV remodelling.

Objective

To assess AR's prevalence and long-term prognostic implications in patients with HFpEF.

Methods

The study population consisted of 458 consecutive patients (age 77.5 ± 9.2 y, 57.9% females) hospitalized with de novo or worsened HFpEF. Patients with more than moderate aortic and/or mitral valve disease were excluded. Data on cardiovascular death, HF re-hospitalization and their composite (MACE) were collected.

Results

Out of 309 (67.5%) patients with any AR, 156 (34.0%) and 153 (33.5%) had mild-AR and moderate-AR, respectively. The remaining 149 (32.5%) individuals had no-AR. Patients with versus without AR were significantly older with larger LV and LA volumes and a higher prevalence of diastolic dysfunction (all p &lt; 0.05). During a median follow-up of 33 ± 25 months, a total of 114 patients (24.9%) died from cardiovascular causes, 126 patients (27.5%) were re-hospitalized for HF, while 272 (59.4%) had the composite endpoint (MACE). In multivariable Cox regression analysis, any AR emerged as an only independent predictor of MACE (HR=1.90, 95%CI 1.26–2.87, p=0.002). Mild-AR and Moderate AR increased the risk of MACE by 77% and 92%, respectively, compared to the No-AR.

Conclusions

In patients with HFpEF, mild-to-moderate AR is highly prevalent, and it seems to identify individuals with worse long-term outcomes. This suggests that even mild AR should be considered a high-risk prognostic marker in patients with HFpEF.

Saline-induced coronary hyperemia with continuous intracoronary thermodilution is mediated by intravascular hemolysis

Objectives

To test whether local hemolysis is a potential mechanism of saline-induced coronary hyperemia.

Background

Absolute coronary flow can be measured by intracoronary continuous thermodilution of saline through the lateral side holes of a dedicated infusion cathete. A saline infusion rate at 15–20 mL/min induces an immediate, steady-state, maximal microvascular vasodilation. The mechanism of this hyperemic response remains unclear.

Methods

Twelve patients undergoing left and right catheterization were included. The left coronary artery and the coronary sinus were selectively cannulated. Absolute resting and hyperemic coronary flow were measured by continuous intracoronary thermodilution. Arterial and venous samples were collected from the coronary artery and the coronary sinus in five phases: baseline (BL); resting flow measurement (Rest, saline infusion at 10 mL/min); hyperemia (Hyperemia,saline infusion at 20 mL/min); post-hyperemia (Post-Hyperemia, two minutes after the cessation of saline infusion); and control phase (Control, during infusion of saline through the guide catheter at 30 mL/min).

Results

Hemolysis was visually detected only in the centrifugated venous blood samples collected during the Hyperemia phase. As compared to Rest, during Hyperemia both LDH (131.50±21.89 U/dL [Rest] and 258.33±57.40 U/dL [Hyperemia], p&lt;0.001) and plasma free hemoglobin (PFHb, 4.92±3.82 mg/dL [Rest] and 108.42±46.58 mg/dL [Hyperemia], p&lt;0.001) significantly increased in the coronary sinus. The percentage of hemolysis was significantly higher during the Hyperemia phase (0.04±0.02% [Rest] vs 0.89±0.34% [Hyperemia], p&lt;0.001).

Conclusions

Saline-induced hyperemia through a dedicated intracoronary infusion catheter is associated with hemolysis. Vasodilatory compounds released locally, like ATP, are likely ultimately responsible for localized microvascular vasodilation.

Funding Acknowledgement

Type of funding sources: None.

Microvascular Dysfunction in Patients With Type II Diabetes Mellitus: Invasive Assessment of Absolute Coronary Blood Flow and Microvascular Resistance Reserve

Background: Coronary microvascular dysfunction (CMD) is an early feature of diabetic cardiomyopathy, which usually precedes the onset of diastolic and systolic dysfunction. Continuous intracoronary thermodilution allows an accurate and reproducible assessment of absolute coronary blood flow and microvascular resistance thus allowing the evaluation of coronary flow reserve (CFR) and Microvascular Resistance Reserve (MRR), a novel index specific for microvascular function, which is independent from the myocardial mass. In the present study we compared absolute coronary flow and resistance, CFR and MRR assessed by continuous intracoronary thermodilution in diabetic vs. non-diabetic patients. Left atrial reservoir strain (LASr), an early marker of diastolic dysfunction was compared between the two groups. Methods: In this observational retrospective study, 108 patients with suspected angina and non-obstructive coronary artery disease (NOCAD) consecutively undergoing elective coronary angiography (CAG) from September 2018 to June 2021 were enrolled. The invasive functional assessment of microvascular function was performed in the left anterior descending artery (LAD) with intracoronary continuous thermodilution. Patients were classified according to the presence of DM. Absolute resting and hyperemic coronary blood flow (in mL/min) and resistance (in WU) were compared between the two cohorts. FFR was measured to assess coronary epicardial lesions, while CFR and MRR were calculated to assess microvascular function. LAS, assessed by speckle tracking echocardiography, was used to detect early myocardial structural changes potentially associated with microvascular dysfunction. Results: The median FFR value was 0.83 [0.79-0.87] without any significant difference between the two groups. Absolute resting and hyperemic flow in the left anterior descending coronary were similar between diabetic and non-diabetic patients. Similarly, resting and hyperemic resistances did not change significantly between the two groups. In the DM cohort the CFR and MRR were significantly lower compared to the control group (CFR = 2.38 ± 0.61 and 2.88 ± 0.82; MRR = 2.79 ± 0.87 and 3.48 ± 1.02 for diabetic and non-diabetic patients respectively, [p < 0.05 for both]). Likewise, diabetic patients had a significantly lower reservoir, contractile and conductive LAS (all p < 0.05). Conclusions: Compared with non-diabetic patients, CFR and MRR were lower in patients with DM and non-obstructive epicardial coronary arteries, while both resting and hyperemic coronary flow and resistance were similar. LASr was lower in diabetic patients, confirming the presence of a subclinical diastolic dysfunction associated to the microcirculatory impairment. Continuous intracoronary thermodilution-derived indexes provide a reliable and operator-independent assessment of coronary macro- and microvasculature and might potentially facilitate widespread clinical adoption of invasive physiologic assessment of suspected microvascular disease.