Coronary Slow-Flow Phenomenon as an Underrecognized and Treatable Source of Chest Pain: Case Series and Literature Review

[Stress-Echocardiography in Low-risk Acute Coronary Syndrome Without Persistent ST-segment Elevation Diagnostic Algorithm]

This review addresses the capabilities of stress EchoCG as a simple, non-invasive, non-radiation method for diagnosing occult disorders of coronary blood flow in patients with non-ST-elevation acute coronary syndrome on a low-risk electrocardiogram. The capabilities of the enhanced stress EchoCG protocol are based on supplementing the standard detection of transient disturbances of local contractility, generally associated with coronary artery obstruction, with an assessment of the heart rate reserve, coronary reserve and other parameters. This approach is considered promising for a more complete characterization of heart function during exercise and an accurate prognosis of the clinical case, which allows determining the tactics for patient management not limited to selection for myocardial revascularization.

Hidden Coronary Atherosclerosis Assessment but Not Coronary Flow Reserve Helps to Explain the Slow Coronary Flow Phenomenon in Patients with Angiographically Normal Coronary Arteries

The significance of the slow coronary flow phenomenon (SCFph), as visualized in patients (pts) with angiographically normal coronary arteries, is controversial. Absolute coronary flow reserve (CFR) in the left anterior descending coronary artery (LAD), non-invasively assessed by a transthoracic color-guided pulsed-wave Doppler (E-Doppler TTE), is a reliable parameter to assess coronary microcirculatory dysfunction (CMD). Mild and angiographically hidden epicardial atherosclerosis (Hath), as visualized by intracoronary ultrasound (IVUS), which could be the clue to atherosclerotic coronary microvascular involvement, has never been investigated together with CFR in patients. This study was aimed at assessing the value of CFR and HA in explaining the SCFph. Methods. Both non-invasive assessment of CFR in the LAD and corrected TIMI frame count assessment of the coronary contrast runoff were performed in 124 pts with angiographically normal coronary arteries. Among the whole group, 32 patients also underwent intracoronary ultrasounds in the LMCA and LAD, and the maximal plaque burden was assessed (Lesion external elastic (EEM) cross sectional area (CSA)—Lesion Lumen CSA/Lesion EEM CSA * 100). We found that 24 of the 124 pts (group 1) had the SCFph and the remaining 100 had a normal runoff (group 2). CFR, evaluated in both groups, was not significantly different, being 2.79 ± 0.79 (Mean ± SD) in group 1 and 2.90 ± 0.8 in group 2 (p = ns); in the pts also examined by IVUS (32 pts), the SCFph was always associated with hidden atherosclerosis, and a plaque burden of ≥33%. On the contrary, in the normal runoff group, any grade of PB was observed (from no athero to a PB > 70%) and remarkably, 10 pts had no signs of athero or just a minimal plaque burden. This resulted in a ROC curve analysis in which PB < 33% had a high negative predictive value (100%) in ruling out the SCFph. In addition, considering a CFR value < 2.21 as an index of coronary microcirculatory dysfunction, we found CMD in 15 pts (15%) in group 1 and in 7 pts (29%) in group 2 (p = ns). In conclusion, the SCFph is strongly connected to epicardial athero to the extent that the absence of hidden coronary athero has a very high negative predictive power in ruling out SCFph. CFR that is based on an endothelium-independent mechanism remains fairly normal in this condition. An endothelium-dependent microcirculatory constriction at rest due to atherosclerotic involvement of the coronary microvascular network is a possible explanation of the SCFph.

Factors Determining Primary Coronary Slow Flow Phenomenon among Opium Users and Non-users: A Case Control Study in Northern Iran

Background

Coronary slow flow phenomenon (CSFP) represents a clinical entity with recurrent chest pain leading to living impairment. The present study aimed to investigate whether opium use correlates with primary CSFP.

Methods

This study included Iranian patients with suspected coronary artery disease who underwent myocardial perfusion imaging. Coronary blood flow was measured quantitatively using the thrombolysis in myocardial infarction (TIMI) frame count and slow flow was defined as TIMI grade 2 standard deviations. Age and clinical conditions including diabetes mellitus (DM), hypertension (HTN), hyperlipidemia (HLP), history of chest pain, and opium use were recorded. First, the characteristics of the two groups were compared and then the main analyses were conducted to examine the relationship between CSFP and opium use. Data were analyzed using t test and chi-square test via SPSS 25.0. The significance level was set at P<0.05.

Findings

This study was conducted on 44 male patients with documented CSFP who had no stenotic lesions and 134 control group male patients who had normal coronary arteries with normal flow. The mean age was similar in the two groups (54.25 vs.52.69, P=0.474). Two groups were significantly different in terms of history of chest pain (P=0.003), but there was no significant difference in HTN (P=0.084), DM (P=0.284), HLP (P=0.183), smoking (P=0.696), and opium use (P=0.107).

Conclusion

This study indicated that opium use is not associated with primary CSFP.

Slow Coronary Blood Flow: Pathogenesis and Clinical Implications

Coronary slow flow (CSF) phenomenon, also known as cardiac syndrome Y, is defined as the delayed opacification of the coronary vasculature at the distal level. Different hypotheses and theories have been postulated about its substrate and mechanism, such as microvascular and endothelial dysfunction. Several studies have confirmed that CSF is a cause of ischaemia detected by non-invasive testing. Clinically, it can present as angina pectoris, acute coronary syndrome and sudden cardiac death. It has an incidence of 1–5% in patients undergoing coronary angiography and has been most frequently found in young men who are smokers with metabolic syndrome. There are no established treatments for CSF and further studies are still necessary.

The relationship between triglyceride/high-density lipoprotein cholesterol ratio and coronary slow-flow phenomenon

In this study, we aimed to investigate the relationship between high triglyceride (TG)/high-density lipoprotein cholesterol (HDL-C) ratio and coronary slow flow phenomenon (CSFP) in patients undergoing elective coronary angiography for suspected coronary artery disease. This prospective study included a total of 84 CSFP patients and 83 controls with normal coronary flow, as evidenced by coronary angiography. The Thrombolysis in Myocardial Infarction (TIMI) frame count (TFC) was used to measure the coronary blood flow velocity. The lipid profiles were analyzed and TG/HDL-C ratio were calculated dividing absolute TG levels by absolute HDL-C levels in peripheral blood. The median TG/HDL-C ratio was higher in the CSFP group than the control group (3.4 [2.6 to 4.9] vs. 2.3 [1.8 to 3], respectively; p < 0.001). The multivariate logistic regression analysis revealed that TG/HDL-C ratio was an independent predictor of CSFP (odds ratio [OR] 1.78, 95% confidence interval [CI] 1.59-2.32; p = 0.001) and TG/HDL-C ratio was positively correlated with the TFC in the CSFP group (r = 0.311, p < 0.001). The area under the receiver operating characteristic curve of TG/HDL-C for the diagnosis of CSFP was 0.73 (95% CI 0.65-0.81; p < 0.001). If a cut-off value of 2.75 was used, higher levels of TG/HDL-C ratio could predict the presence of CSFP with 72% sensitivity and 71% specificity. Our study results suggest that TG/HDL-C ratio is associated with CSFP and may be a useful biomarker for predicting CSFP and its severity.

miRNA-22 as a Candidate Diagnostic Biomarker for Coronary Slow Flow

Background

Coronary slow flow (CSF) refers to the phenomenon of delayed distal flow in the absence of lesions detected on coronary angiography. Although the detection rate of CSF has been increasing in clinical practice, early diagnosis is difficult and the factors contributing to this condition remain unclear. Given the increasing demonstration of the roles of microRNAs (miRNAs) in disease and as diagnostic biomarkers, the aim of this study was to analyze the expression of serum miRNA-22 in patients with CSF detected using coronary angiography and its diagnostic efficacy.

Methods and Results

A retrospective analysis including 44 patients with CSF and 42 patients with normal coronary flow (control group) was conducted. Additionally, all included patients either did not have visually estimated coronary artery stenosis or had <50% stenosis. Plasma samples were collected from patients in these two groups, and the levels of miRNA-22 were detected. The receiver operating characteristic (ROC) curve was plotted to evaluate the diagnostic efficiency of serum miRNA-22 in the context of CSF.

Results

The expression of serum miRNA-22 was significantly higher in the CSF patients than in the control subjects (P < 0.0001). The area under the ROC curve for miRNA-22 in diagnosing CSF was 0.8293 (95% confidence interval: 0.7313–0.9272), with a sensitivity of 75.0% and specificity of 88.1%.

Conclusions

The expression of serum miRNA-22 in CSF is upregulated compared to that in subjects with normal coronary flow and shows relatively high clinical diagnostic efficiency, suggesting a new potential biomarker for the early diagnosis of CSF.

Ventricular Dysfunction in Patients with Coronary Slow-Flow Phenomenon: A Single-center Case-control Study

Background:

Coronary slow-flow phenomenon (CSFP), characterized by delayed distal vessel opacification of contrast, in the absence of significant epicardial coronary stenosis, has effects on exercise capacity and clinical outcomes. The aim of this study was to explore the systolic and diastolic function of patients with CSFP and to compare it with a group of controls with normal coronary anatomy and flow.

Materials and Methods:

In this case–control study, 45 consecutive CSFP patients and 45 age-, body mass index-, and presentation season-matched controls with normal coronary arteries and normal coronary flows were enrolled from Seyyedoshohada Heart Center from March 2015 to March 2016. A transthoracic echocardiography was done by a blinded echocardiographer using both conventional and tissue Doppler imaging techniques.

Results:

Patients with CSFP were more likely to be male (P = 0.006) and smoker (P = 0.02) compared to controls. Other risk factors were not different between the two groups. There were no differences between groups in terms of the peak early (E) and late (A) diastolic velocities, deceleration time, early (E’) and late (A’) peak diastolic velocities at the mitral annulus, and the systolic mitral annular velocity (S’). Global longitudinal strain and peak systolic strain rates was lower in patients with CSFP compared to controls (−16.7% ±2.4% vs. −18.9% ±1.6%, P < 0.001 and 1.10 ± 0.1 vs. 1.24 ± 0.3, P = 0.008, respectively).

Conclusion:

Patients with CSFP showed signs of the left ventricular systolic dysfunction in tissue Doppler echocardiography, which underlines the importance of close follow-up in these patients. Patients with CSFP should be screened for ventricular function preferably by tissue Doppler echocardiography.

Assessment of Coronary Slow Flow, Cystatin C, and Body Mass Index in Female Candidates for Diagnostic Coronary Artery Angiography

Introduction: Evidence indicates that the associations between coronary slow flow (CSF), cystatin C (Cys C), and body mass index (BMI) are unclear. Therefore, the purpose of our study was to determine the association among the above-mentioned parameters in female patients. Methods: This was a descriptive-analytical study and the participants were those who were referred to the Shohada Cardiovascular Center of Urmia in 2015-2016. The participants were measured by a quantitative method under angiography (corrected TIMI frame count, CTFC) for CSF assessment, followed by evaluating physiological indices and the serum Cys C by the enzyme-linked immunosorbent assay. Finally, Pearson correlation coefficient test was used to analyze the correlations among CTFC, Cys C, and BMI, and a significance level of P < 0.05 was used for this test. Results: Sixty-six female patients (mean age: 57.01±8.25 years) took part in this study. The correlations among Cys C with CTFC, and BMI (r=-0.189, P=0.128 and r=0.044, P=0.724, respectively) and BMI with CTFC (r=-0.178, P=0.153) were not meaningful in female patients’ who were candidates for angiography. Conclusion: In general, the results suggested that serum Cys C cannot be considered as a predictive biomarker for the prognostic stratification of CSF and BMI in female patients aged 34-73 years who were candidates for angiography.

Myocardial Infarction Secondary to Marijuana-Induced Coronary Vasospasm

With the rise of the number of states fully legalizing marijuana, the use of this substance in the United States is at an all-time high. This increasing legalization gives the impression that marijuana is rather safe. However, multiple reports by our groups and others documented serious cardiovascular complications associated with marijuana use ranging from life threatening arrhythmia to myocarditis and myocardial infarction. In this report, we present a case of a 61 year old man presented with left sided typical chest pain shortly after marijuana consumption with the diagnosis of non ST-elevation myocardial infarction (NSTEMI) established based on clinical, EKG and troponin values with eventual cardiac catheterization documenting non-occlusive coronary artery disease with 30% obstruction of the proximal first obtuse marginal artery. We also review the putative pathophysiologic mechanisms of marijuana induced coronary vasospasms, highlighting the implications of these findings in the evaluation and management of cardiac chest pain in marijuana users.