Submaximal adenosine‐induced coronary hyperaemia with 12 h caffeine abstinence: implications for clinical adenosine perfusion imaging tests

Protocol Variation in Functional Coronary Angiography Among Patients With Suspected Angina With Non-Obstructive Coronary Arteries: A Nationwide Snapshot of Current Practice Within Australia and New Zealand

BACKGROUND

Functional coronary angiography (FCA) for endotype characterisation (vasospastic angina [VSA], coronary microvascular disease [CMD], or mixed) is recommended among patients with angina with non-obstructive coronary arteries. Whilst clear diagnostic criteria for VSA and CMD exist, there is no standardised FCA protocol. Variations in testing protocol may limit the widespread uptake of testing, generalisability of results, and expansion of collaborative research. At present, there are no data describing protocol variation across an entire geographic region. Therefore, we aimed to capture current practice variations in the approach to FCA to improve access and standardisation for diagnosis of coronary vasomotor disorders in Australia and New Zealand.

METHOD

Between July 2022 and July 2023, we conducted a national survey across all centres in Australia and New Zealand with an active FCA program. The survey captured attitudes towards FCA and protocols used for diagnosis of coronary vasomotor disorders at 33 hospitals across Australia and New Zealand.

RESULTS

Survey responses were received from 39 clinicians from 33 centres, with representation from centres within all Australian states and territories and both North and South Islands of New Zealand. A total of 21 centres were identified as having an active FCA program. In general, respondents agreed that comprehensive physiology testing helped inform clinical management. Barriers to program expansion included cost, additional catheter laboratory time, and the absence of an agreed-upon national protocol. Across the clinical sites, there were significant variations in testing protocol, including the technique used (Doppler vs thermodilution), order of testing (hyperaemia resistance indices first vs vasomotor function testing first), rate and dose of acetylcholine administration, routine use of temporary pacing wire, and routine single vs multivessel testing. Overall, testing was performed relatively infrequently, with very little follow-on FCA performed, despite nearly all respondents believing this would be clinically useful.

CONCLUSIONS

This survey demonstrates, for the first time, variations in FCA protocol among testing centres across two entire countries. Furthermore, whilst FCA was deemed clinically important, testing was performed relatively infrequently with little or no follow-on testing. Development and adoption of a standardised national FCA protocol may help improve patient access to testing and facilitate further collaborative research within Australia and New Zealand.

Timing of Regadenoson-induced Peak Hyperemia and the Effects on Coronary Flow Reserve

Background

Regadenoson is used to induce hyperemia in cardiac imaging, facilitating diagnosis of ischemia and assessment of coronary flow reserve (CFR). While the regadenoson package insert recommends administration of radionuclide tracer 10-20 seconds after injection, peak hyperemia has been observed at approximately 100 seconds after injection in healthy volunteers undergoing cardiovascular magnetic resonance imaging (CMR). It is unclear when peak hyperemia occurs in a patient population.

Objectives

The goal of this study was to determine time to peak hyperemia after regadenoson injection in healthy volunteers and patients, and whether the recommended image timing in the package insert underestimates CFR.

Methods

Healthy volunteers (n=15) and patients (n=25) underwent stress CMR, including phase-contrast imaging of the coronary sinus at rest and multiple timepoints after 0.4 mg regadenoson injection. Coronary sinus flow (ml/min) was divided by resting values to yield CFR. Smoothed, time-resolved curves for CFR were generated with pointwise 95% confidence intervals.

Results

CFR between 60 and 120 seconds was significantly higher than CFR at 30 seconds after regadenoson injection (p < 0.05) as shown by non-overlapping 95% confidence intervals for both healthy volunteers (30 s, [2.8, 3.4]; 60 s, [3.8, 4.4]; 90 s, [4.1, 4.7]; 120 s, [3.6, 4.3]) and patients (30 s, [2.1, 2.5]; 60 s, [2.6, 3.1]; 90 s, [2.7, 3.2]; 120 s, [2.5, 3.1]).

Conclusion

Imaging at 90 seconds following regadenoson injection is the optimal approach to capture peak hyperemia. Imaging at 30 seconds, which is more aligned with the package insert recommendation, would yield an underestimate of CFR and confound assessment of microvascular dysfunction.

Quantitative myocardial perfusion should be interpreted in the light of sex and comorbidities in patients with suspected chronic coronary syndrome: A cardiac positron emission tomography study

Diagnosis and treatment of patients with suspected chronic coronary syndrome (CCS) currently relies on the degree of coronary artery stenosis and its significance for myocardial perfusion. However, myocardial perfusion can be affected by factors other than coronary stenosis. The aim of this study was to investigate to what extent sex, age, diabetes, hypertension and smoking affect quantitative myocardial perfusion, beyond the degree of coronary artery stenosis, in patients with suspected or established CCS. Eighty-six patients [median age 69 (range 46-86) years, 24 females] planned for elective coronary angiography due to suspected or established CCS were included. All patients underwent cardiac 13 N-NH3 positron emission tomography to quantify myocardial perfusion at rest and stress. Lowest myocardial perfusion (perfusionmin ) at stress and rest and lowest myocardial perfusion reserve (MPRmin ) for all vessel territories was used as dependent variables in a linear mixed model. Independent variables were vessel territory, degree of coronary artery stenosis (as a continuous variable of 0%-100% stenosis), sex, age, diabetes, hypertension and smoking habits. Degree of coronary artery stenosis (p < 0.001), male sex (1.8 ± 0.6 vs. 2.3 ± 0.6 mL/min/g, p < 0.001), increasing age (p = 0.025), diabetes (1.6 ± 0.5 vs. 2.0 ± 0.6 mL/min/g, p = 0.023) and smoking (1.9 ± 0.6 vs. 2.1 ± 0.6 mL/min/g, p = 0.052) were independently associated with myocardial perfusionmin at stress. Degree of coronary artery stenosis (p < 0.001), age (p = 0.040), diabetes (1.8 ± 0.6 vs. 2.3 ± 0.7, p = 0.046) and hypertension (2.2 ± 0.7 vs. 2.5 ± 0.6, p = 0.033) were independently associated with MPRmin . Sex, increasing age, diabetes, hypertension and smoking affect myocardial perfusion independent of coronary artery stenosis in patients with suspected or established CCS. Thus, these factors need to be considered when assessing the significance of reduced quantitative myocardial perfusion of patients with suspected or established CCS.

Coronary flow reserve evaluated by phase-contrast cine cardiovascular magnetic resonance imaging of coronary sinus: a meta-analysis

BACKGROUND

Phase-contrast cine cardiovascular magnetic resonance (CMR) of the coronary sinus has emerged as a non-invasive method for measuring coronary sinus blood flow and coronary flow reserve (CFR). However, its clinical utility has not yet been established. Here we performed a meta-analysis to clarify the clinical value of CMR-derived CFR in various cardiovascular diseases.

METHODS

An electronic database search was performed of PubMed, Web of Science Core Collection, Cochrane Advanced Search, and EMBASE. We compared the CMR-derived CFR of various cardiovascular diseases (stable coronary artery disease [CAD], hypertrophic cardiomyopathy [HCM], dilated cardiomyopathy [DCM]) and control subjects. We assessed the prognostic value of CMR-derived CFR for predicting major adverse cardiac events (MACE) in patients with stable CAD.

RESULTS

A total of 47 eligible studies were identified. The pooled CFR from our meta-analysis was 3.48 (95% confidence interval [CI], 2.98-3.98) in control subjects, 2.50 (95% CI, 2.38-2.61) in stable CAD, 2.01 (95% CI, 1.70-2.32) in cardiomyopathies (HCM and DCM). The meta-analysis showed that CFR was significantly reduced in stable CAD (mean difference [MD] = -1.48; 95% CI, -1.78 to -1.17; p < 0.001; I2 = 0%; p for heterogeneity = 0.33), HCM (MD = -1.20; 95% CI, -1.63 to -0.77; p < 0.001; I2 = 0%; p for heterogeneity = 0.49), and DCM (MD = -1.53; 95% CI, -1.93 to -1.13; p < 0.001; I2 = 0%; p for heterogeneity = 0.45). CMR-derived CFR was an independent predictor of MACE for patients with stable CAD (hazard ratio = 0.52 per unit increase; 95% CI, 0.37-0.73; p < 0.001; I2 = 84%, p for heterogeneity < 0.001).

CONCLUSIONS

CMR-derived CFR was significantly decreased in cardiovascular diseases, and a decreased CFR was associated with a higher occurrence of MACE in patients with stable CAD. These results suggest that CMR-derived CFR has potential for the pathological evaluation of stable CAD, cardiomyopathy, and risk stratification in CAD.

Quantitative myocardial perfusion during stress using CMR is impaired in healthy Middle Eastern immigrants without CV risk factors

Middle Eastern immigrants constitute a growing proportion of the European population and compared to native Swedes are more insulin resistant, which can contribute to atherosclerosis. Quantitative first pass perfusion (qFPP) using cardiovascular magnetic resonance (CMR) can detect early signs of cardiovascular disease (CVD). The aim was to study if myocardial perfusion differs between healthy male Middle Eastern immigrants and native male Swedes. Eighteen Iraqi- and twelve Swedish born controls, all males, never smokers with no CVD risk factors were included. Global myocardial perfusion at rest and stress was assessed using qFPP and by phase-contrast CMR imaging of coronary sinus flow. Quantitative first pass perfusion analysis (mean ± SD) demonstrated no difference at rest between Iraqi and Swedish males (0.8 ± 0.2 vs 1.0 ± 0.4 ml/min/g, P = 0.38) but lower perfusion during adenosine in Iraqi males (2.9 ± 0.7 vs 3.5 ± 0.7 ml/min/g, P = 0.02). Myocardial perfusion assessed by coronary sinus flow demonstrated similar results with no difference in resting perfusion between groups (0.7 ± 0.2 vs 0.8 ± 0.2 ml/min/g, P = 0.21) but a lower perfusion during adenosine in the Iraqi group (3.0 ± 0.2 vs 3.7 ± 0.6 ml/min/g, P = 0.01. Myocardial perfusion during adenosine stress was lower in healthy Iraqi immigrants compared to Swedish controls suggesting impaired microvascular function and risk of underestimating CVD risk in healthy individuals of Middle Eastern origin.

Myocardial perfusion by CMR coronary sinus flow shows sex differences and lowered perfusion at stress in patients with suspected microvascular angina

Background

Methods

Results

Conclusions

Aging increases circulating BH2 without modifying BH4 levels and impairs peripheral vascular function in healthy adults

Little is known about the mechanisms of aging on vascular beds and its relationship with tetra and di-hydrobiopterin (BH4 and BH2) levels. This observational clinical study analyzed the impact of aging on plasma and platelet biopterins, cutaneous blood flow (CBF), and coronary flow reserve (CFR) in healthy adults. The study enrolled healthy adults in 3 age groups: 18-30, 50-59, and 60-70 years (n = 25/group). Biopterins were assessed by LC-MS/MS using newly defined pre-analytical conditions limiting BH4 oxidation and improving long-term stability. CBF was measured by Laser Speckle Contrast Imaging coupled with acetylcholine-iontophoresis and CFR by adenosine stress cardiac magnetic resonance. In healthy adults, aging (60-70 years vs 18-30 years) significantly increased platelet BH2 (+75%, P = 0.033) and BH2 + BH4 (+31%, P = 0.033), and to a lesser extent plasma BH2 (+29%, P = 0.009) without affecting BH4 and BH4/BH2. Simultaneously, CBF was decreased (-23%, P = 0.004) but not CFR, CBF being inversely correlated with platelet BH2 (r = -0.42, P = 0.001) and BH2 + BH4 (r = -0.41, P = 0.002). The proportion of adults with abnormal platelet BH2 increased with age (+28% in 60-70y). These abnormal BH2 levels were significantly associated with reduced CBF and CFR (-16%, P = 0.03 and -26%, P = 0.02). In conclusion, our study showed that age-related peripheral endothelial dysfunction was associated with an increase in circulating BH2 without decreasing BH4, the effect being more marked in platelets, the most relevant blood compartment to assess biopterin bioavailability. Peripheral but not coronary vascular function is progressively impaired with aging in healthy adults. All these findings support biopterins as therapeutic targets to improve vascular function.

Doppler Echocardiography Assessment of Coronary Microvascular Function in Patients With Angina and No Obstructive Coronary Artery Disease

Echocardiographic evaluation is an essential part of the diagnostic work-up in patients with known or suspected cardiovascular disease. Transthoracic Doppler echocardiography (TTDE) enables straightforward and reliable visualization of flow in the left anterior descending artery. In the absence of obstructive coronary artery disease, low TTDE-derived coronary flow velocity reserve (CFVR) is considered a marker of coronary microvascular dysfunction (CMD). TTDE CFVR is free from ionizing radiation and widely available, utilizing high-frequency transducers, pharmacologic vasodilator stress, and pulsed-wave Doppler quantification of diastolic peak flow velocities. European Society of Cardiology guidelines recommend TTDE CFVR evaluation only following preceding anatomic invasive or non-invasive coronary imaging excluding obstructive CAD. Accordingly, clinical use of TTDE CFVR is limited and CMD frequently goes undiagnosed. An evolving body of evidence underlines that low CFVR is an important and robust predictor of adverse prognosis and continuing symptoms in angina patients both with and without obstructive CAD. The majority of angina patients have no obstructive CAD, particularly among women. This has led to the suggestion that there may be a gender-specific female atherosclerotic phenotype with less epicardial obstruction, and a low CFVR signifying CMD instead. Nevertheless, available evidence indicates low CFVR is an equally important prognostic marker in both men and women. In this review, TTDE CFVR was evaluated regarding indication, practical and technical aspects, and interpretation of results. Association with symptoms and prognosis, comparison with alternative invasive and non-invasive imaging modalities, and possible interventions in angina patients with low CFVR were discussed, and key research questions were proposed.

Cardiac hypoxic resistance and decreasing lactate during maximum apnea in elite breath hold divers

Breath-hold divers (BHD) enduring apnea for more than 4 min are characterized by resistance to release of reactive oxygen species, reduced sensitivity to hypoxia, and low mitochondrial oxygen consumption in their skeletal muscles similar to northern elephant seals. The muscles and myocardium of harbor seals also exhibit metabolic adaptations including increased cardiac lactate-dehydrogenase-activity, exceeding their hypoxic limit. We hypothesized that the myocardium of BHD possesses similar adaptive mechanisms. During maximum apnea ¹⁵O-H₂O-PET/CT (n = 6) revealed no myocardial perfusion deficits but increased myocardial blood flow (MBF). Cardiac MRI determined blood oxygen level dependence oxygenation (n = 8) after 4 min of apnea was unaltered compared to rest, whereas cine-MRI demonstrated increased left ventricular wall thickness (LVWT). Arterial blood gases were collected after warm-up and maximum apnea in a pool. At the end of the maximum pool apnea (5 min), arterial saturation decreased to 52%, and lactate decreased 20%. Our findings contrast with previous MR studies of BHD, that reported elevated cardiac troponins and decreased myocardial perfusion after 4 min of apnea. In conclusion, we demonstrated for the first time with ¹⁵O-H₂O-PET/CT and MRI in elite BHD during maximum apnea, that MBF and LVWT increases while lactate decreases, indicating anaerobic/fat-based cardiac-metabolism similar to diving mammals.

MRI perfusion in patients with stable chest-pain

Perfusion-cardiovascular MR (CMR) imaging has been shown to reliably identify patients with suspected or known coronary artery disease (CAD), who are at risk for future cardiac events and thus, allows for guiding therapy including revascularizations. Accordingly, it is an ideal test to exclude prognostically relevant coronary artery disease. Several guidelines, such as the ESC guidelines, currently recommend CMR as non-invasive testing in patients with stable chest pain. CMR has as an advantage over the more conventional pathways as it lacks radiation and it potentially reduces costs.

Females have higher myocardial perfusion, blood volume and extracellular volume compared to males - an adenosine stress cardiovascular magnetic resonance study

Knowledge on sex differences in myocardial perfusion, blood volume (MBV), and extracellular volume (ECV) in healthy individuals is scarce and conflicting. Therefore, this was investigated quantitatively by cardiovascular magnetic resonance (CMR). Healthy volunteers (n = 41, 51% female) underwent CMR at 1.5 T. Quantitative MBV [%] and perfusion [ml/min/g] maps were acquired during adenosine stress and at rest following an intravenous contrast bolus (0.05 mmol/kg, gadobutrol). Native T1 maps were acquired before and during adenosine stress, and after contrast (0.2 mmol/kg) at rest and during adenosine stress, rendering rest and stress ECV maps. Compared to males, females had higher perfusion, ECV, and MBV at stress, and perfusion and ECV at rest (p < 0.01 for all). Multivariate linear regression revealed that sex and MBV were associated with perfusion (sex beta −0.31, p = 0.03; MBV beta −0.37, p = 0.01, model R² = 0.29, p < 0.01) while sex and hematocrit were associated with ECV (sex beta −0.33, p = 0.03; hematocrit beta −0.48, p < 0.01, model R² = 0.54, p < 0.001). Myocardial perfusion, MBV, and ECV are higher in female healthy volunteers compared to males. Sex is an independent contributor to perfusion and ECV, beyond other physiological factors that differ between the sexes. These findings provide mechanistic insight into sex differences in myocardial physiology.

Computed tomography for myocardial characterization in ischemic heart disease: a state-of-the-art review

This review provides an overview of the currently available computed tomography (CT) techniques for myocardial tissue characterization in ischemic heart disease, including CT perfusion and late iodine enhancement. CT myocardial perfusion imaging can be performed with static and dynamic protocols for the detection of ischemia and infarction using either single- or dual-energy CT modes. Late iodine enhancement may be used for the analysis of myocardial infarction. The accuracy of these CT techniques is highly dependent on the imaging protocol, including acquisition timing and contrast administration. Additionally, the options for qualitative and quantitative analysis and the accuracy of each technique are discussed.

Impact of caffeine on myocardial perfusion reserve assessed by semiquantitative adenosine stress perfusion cardiovascular magnetic resonance

BACKGROUND

Adenosine is used in stress perfusion cardiac imaging to reveal myocardial ischemia by its vasodilator effects. Caffeine is a competitive antagonist of adenosine. However, previous studies reported inconsistent results about the influence of caffeine on adenosine's vasodilator effect. This study assessed the impact of caffeine on the myocardial perfusion reserve index (MPRI) using adenosine stress cardiovascular magnetic resonance imaging (CMR). Moreover, we sought to evaluate if the splenic switch-off sign might be indicative of prior caffeine consumption.

METHODS

Semiquantitative perfusion analysis was performed in 25 patients who underwent: 1) caffeine-naïve adenosine stress CMR demonstrating myocardial ischemia and, 2) repeat adenosine stress CMR after intake of caffeine. MPRI (global; remote and ischemic segments), and splenic perfusion ratio (SPR) were assessed and compared between both exams.

RESULTS

Global MPRI after caffeine was lower vs. caffeine-naïve conditions (1.09 ± 0.19 vs. 1.24 ± 0.19; p <  0.01). MPRI in remote myocardium decreased by caffeine (1.24 ± 0.19 vs. 1.49 ± 0.19; p <  0.001) whereas MPRI in ischemic segments (0.89 ± 0.18 vs. 0.95 ± 0.23; p = 0.23) was similar, resulting in a lower MPRI ratio (=remote/ischemic segments) after caffeine consumption vs. caffeine-naïve conditions (1.41 ± 0.19 vs. 1.64 ± 0.35, p = 0.01). The SPR was unaffected by caffeine (SPR 0.38 ± 0.19 vs. 0.38 ± 0.18; p = 0.92).

CONCLUSION

Caffeine consumption prior to adenosine stress CMR results in a lower global MPRI, which is driven by the decreased MPRI in remote myocardium and underlines the need of abstinence from caffeine. The splenic switch-off sign is not affected by prior caffeine intake.

Heart filling exceeds emptying during late ventricular systole in patients with systolic heart failure and healthy subjects - a cardiac MRI study

Background

Total heart volume (THV) within the pericardium is not constant throughout the cardiac cycle and THV would intuitively be lowest at end systole. We have, however, observed a phase shift between ventricular outflow and atrial inflow which causes the minimum THV to occur before end systole. The aims were to explain the mechanism of the late‐systolic net inflow to the heart and determine whether this net inflow is affected by increased cardiac output or systolic heart failure.

Methods and Results

Healthy controls (n = 21) and patients with EF<35% (n = 14) underwent magnetic resonance imaging with flow measurements in vessels to and from the heart, and this was repeated in nine controls during 140 μgram kg⁻¹ min⁻¹ adenosine infusion. Minimum THV occurred 78 ± 6 ms before end of systolic ejection (8 ± 1% of the cardiac cycle) in controls. The late‐systolic net inflow was 12·3 ± 1·1 ml or 6·0 ± 0·5% of total stroke volume (TSV). Cardiac output increased 66 ± 8% during adenosine but late‐systolic net inflow to the heart did not change (P = 0·73). In patients with heart failure, late‐systolic net inflow of the heart′s left side was lower (3·4 ± 0·5%) compared to healthy subjects (5·3 ± 0·6%, P = 0·03).

Conclusions

Heart size increases before end systole due to a late‐systolic net inflow which is unaffected by increased cardiac output. This may be explained by inertia of blood that flows into the atria generated by ventricular systole. The lower late‐systolic net inflow in patients with systolic heart failure may be a measure of decreased ventricular filling due to decreased systolic function, thus linking systolic to diastolic dysfunction.

Controlling for caffeine in cardiovascular research: A critical review

Caffeine, the most widely consumed drug in the world, exerts numerous effects on cardiovascular activity. Thus, it is important and advisable to control for caffeine consumption in studies examining caffeine and/or cardiovascular activity and reactivity. This paper 1) reviews the literature concerning caffeine's effects on cardiovascular parameters; 2) summarizes the widely varying protocols used to control for the drug in extant cardiovascular literature, and 3) provide guidelines for caffeine control procedures to minimize potentially confounding acute and withdrawal effects of the drug. An abstention period equal to the average half-life of the drug is recommended for creation of methodological controls for caffeine. Additional methodological recommendations are described concerning factors that moderate the half-life of caffeine. When feasible, researchers should consider and aim to control for caffeine's acute and extended psychophysiological effects. This understudied issue has fundamental implications for caffeine-related investigations and research in psychophysiology and behavioral medicine.

Effects of Caffeine on Myocardial Blood Flow: A Systematic Review

Background. Caffeine is one of the most widely consumed stimulants worldwide. It is a well-recognized antagonist of adenosine and a potential cause of false-negative functional measurements during vasodilator myocardial perfusion. The aim of this systematic review is to summarize the evidence regarding the effects of caffeine intake on functional measurements of myocardial perfusion in patients with suspected coronary artery disease. Pubmed, Web of Science, and Embase were searched using a predefined electronic search strategy. Participants—healthy subjects or patients with known or suspected CAD. Comparisons—recent caffeine intake versus no caffeine intake. Outcomes—measurements of functional myocardial perfusion. Study design—observational. Fourteen studies were deemed eligible for this systematic review. There was a wide range of variability in study design with varying imaging modalities, vasodilator agents, serum concentrations of caffeine, and primary outcome measurements. The available data indicate a significant influence of recent caffeine intake on cardiac perfusion measurements during adenosine and dipyridamole induced hyperemia. These effects have the potential to affect the clinical decision making by re-classification to different risk-categories.

Decreased global myocardial perfusion at adenosine stress as a potential new biomarker for microvascular disease in systemic sclerosis: a magnetic resonance study

Background

Patients with systemic sclerosis (SSc) have high cardiovascular mortality even though there is no or little increase in prevalence of epicardial coronary stenosis. First-pass perfusion on cardiovascular magnetic resonance (CMR) have detected perfusion defects indicative of microvascular disease, but the quantitative extent of hypoperfusion is not known. Therefore, we aimed to determine if patients with SSc have lower global myocardial perfusion (MP) at rest or during adenosine stress, compared to healthy controls, quantified with CMR.

Methods

Nineteen SSc patients (17 females, 61 ± 10 years) and 22 controls (10 females, 62 ± 11 years) underwent CMR. Twelve patients had limited cutaneous SSc and 7 patients had diffuse cutaneous SSc. One patient had pulmonary arterial hypertension (PAH). MP was quantified using coronary sinus flow (CSF) measurements at rest and during adenosine stress, divided by left ventricular mass (LVM).

Results

There was no difference in MP at rest between patients and controls (1.1 ± 0.5 vs. 1.1 ± 0.3 ml/min/g, P = 0.85) whereas SSc patients showed statistically significantly lower MP during adenosine stress (3.1 ± 0.9 vs. 4.2 ± 1.3 ml/min/g, P = 0.008). Three out of the 19 SSc patients showed fibrosis in the right ventricle insertion points despite absence of PAH. None had signs of myocardial infarction.

Conclusions

Patients with SSc have decreased MP during adenosine stress compared to healthy controls. Thus hypoperfusion at stress may be a sensitive marker of cardiac disease in SSc patients possibly signifying microvascular myocardial disease.

Serum Biomarkers of Myocardial Remodeling and Coronary Dysfunction in Early Stages of Hypertrophic Cardiomyopathy in the Young

Hypertrophic cardiomyopathy (HCM) remains the leading cause of sudden cardiac death in the young. Early markers for HCM are important to identify individuals at risk. The aim of this study was to investigate novel serum biomarkers reflecting myocardial remodeling, microfibrosis, and vascular endotheliopathy in the early stages of familial HCM in young patients. Twenty-three HCM patients, 16 HCM-risk individuals, and 66 controls (median 15 years) underwent echocardiography and serum analysis for cathepsin S, endostatin, myostatin, type I collagen degradation marker (ICTP), matrix metalloproteinase (MMP)-9, vascular endothelial growth factor receptor (VEGFR)-1, and vascular and intercellular adhesion molecules (VCAM, ICAM). In a subset of the population, global myocardial perfusion was performed by magnetic resonance imaging. Cathepsin S (p = 0.0009), endostatin (p < 0.0001), MMP-9 (p = 0.008), and VCAM (p = 0.04) were increased in the HCM group and correlated to left ventricular mass index and mitral E/e' (p < 0.01). In the HCM-risk group, myostatin was decreased (p = 0.004), whereas ICAM was increased (p = 0.002). Global perfusion was decreased in the HCM group (p < 0.05) versus controls. Endostatin and mitral E/e' correlated inversely to myocardial perfusion (p ≤ 0.05). This is the first study demonstrating adverse changes in biomarkers reflecting myocardial matrix remodeling, microfibrosis, and vascular endotheliopathy in early stage of hypertrophic cardiomyopathy in the young.

Stress Cardiac MRI in Women With Myocardial Infarction and Nonobstructive Coronary Artery Disease

BACKGROUND

In a prospective study, cardiac MRI (CMR) and intravascular ultrasound were performed in women with myocardial infarction (MI) and nonobstructive coronary artery disease (MINOCA). Forty participants underwent adenosine-stress CMR (sCMR).

HYPOTHESIS

Abnormal perfusion may co-localize with ischemic late gadolinium enhancement (LGE) and T2-weighted signal hyperintensity (T2+), suggesting microvascular dysfunction contributed to MI.

METHODS

Qualitative perfusion analysis was performed by 2 independent readers. Abnormal myocardial perfusion reserve index (MPRI) was defined as global average ≤1.84.

RESULTS

Abnormal rest perfusion was present in 10 patients (25%) and stress perfusion abnormalities in 25 (63%). Abnormal stress perfusion was not associated with LGE but tended to occur with T2+. Among patients with abnormal perfusion and LGE, the LGE pattern was ischemic in half. The locations of abnormal perfusion and LGE matched in 75%, T2+ in 100%. Abnormal stress perfusion was not associated with plaque disruption and matched in location in 63%. MPRI was abnormal in 10 patients (25%) and was not associated with LGE, T2+ or plaque disruption.

CONCLUSIONS

Abnormal perfusion on sCMR is common among women with MINOCA. Abnormal perfusion usually co-localized with LGE and/or T2+ when present. Variability in LGE pattern leads to uncertainty about whether the finding of abnormal perfusion was cause or consequence of the tissue state leading to LGE. Low MPRI, possibly indicating diffuse microvascular disease, was observed with and without LGE and T2+. Multiple mechanisms may lead to abnormal perfusion on sCMR. Microvascular dysfunction may contribute to the pathogenesis of and coexist with other causes of MINOCA.

Caffeine reduces the sensitivity of vasodilator MPI for the detection of myocardial ischaemia: Pro

Caffeine is a non-selective antagonist at the adenosine receptors, which is expected to reverse both the intended (coronary vasodilation) and unintended (hypotension, flushing) effects of exogenously administered adenosine and adenosine-related compounds. In the past, several studies were conducted to characterize the effect of caffeine on vasodilator myocardial perfusion imaging (MPI) with conflicting results. However, new evidence supports earlier observations and shows that recent caffeine intake attenuates vasodilator-induced myocardial hyperaemia and may therefore reduce the sensitivity of radionuclide MPI for the detection of inducible perfusion abnormality in patients with coronary artery disease. Although the magnitude of this effect and hence its clinical significance are dose dependent, the acute response to equivalent doses of caffeine varies largely among individuals, and this might be explained by differences in caffeine exposure and genetically determined variations in caffeine metabolism. Abstinence from caffeinated foods and beverages for a minimum of 12 hours before vasodilator stress is therefore recommended although longer abstention might be required in order to prevent the potentially blocking effect of residual caffeine on vasodilator-mediated actions.

Regadenoson stress for myocardial perfusion imaging

Noninvasive functional imaging plays a major role in the diagnosis of hemodynamically significant coronary artery disease (CAD) by means of the detection of abnormal myocardial perfusion. For this, cardiac stressors are essential as they induce hypoperfusion in the presence of flow-limiting coronary stenosis. Several pharmacological stressors are currently available and it is important that clinicians who are involved in the care and management of patients with CAD become familiar with their indications, contraindications and protocols. Among the primary coronary vasodilator agents, regadenoson is increasingly used as the default stressor or as an alternative to other modalities of stress. This article provides an updated review of regadenoson stress for the assessment of patients with suspected or known CAD and describes its pharmacological properties, stress protocol, efficacy and safety profile.

An echo-planar imaging sequence is superior to a steady-state free precession sequence for visual as well as quantitative assessment of cardiac magnetic resonance stress perfusion

BACKGROUND

To assess myocardial perfusion, steady-state free precession cardiac magnetic resonance (SSFP, CMR) was compared with gradient-echo-echo-planar imaging (GRE-EPI) using myocardial perfusion scintigraphy (MPS) as reference.

METHODS

Cardiac magnetic resonance perfusion was recorded in 30 patients with SSFP and in another 30 patients with GRE-EPI. Timing and extent of inflow delay to the myocardium was visually assessed. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated. Myocardial scar was visualized with a phase-sensitive inversion recovery sequence (PSIR). All scar positive segments were considered pathologic. In MPS, stress and rest images were used as in clinical reporting. The CMR contrast wash-in slope was calculated and compared with the stress score from the MPS examination. CMR scar, CMR perfusion and MPS were assessed separately by one expert for each method who was blinded to other aspects of the study.

RESULTS

Visual assessment of CMR had a sensitivity for the detection of an abnormal MPS at 78% (SSFP) versus 91% (GRE-EPI) and a specificity of 58% (SSFP) versus 84% (GRE-EPI). Kappa statistics for SSFP and MPS was 0·29, for GRE-EPI and MPS 0·72. The ANOVA of CMR perfusion slopes for all segments versus MPS score (four levels based on MPS) had correlation r = 0·64 (SSFP) and r = 0·96 (GRE-EPI). SNR was for normal segments 35·63 ± 11·80 (SSFP) and 17·98 ± 8·31 (GRE-EPI), while CNR was 28·79 ± 10·43 (SSFP) and 13·06 ± 7·61 (GRE-EPI).

CONCLUSION

GRE-EPI displayed higher agreement with the MPS results than SSFP despite significantly lower signal intensity, SNR and CNR.

Predictors and Diagnostic Significance of the Adenosine Related Side Effects on Myocardial Perfusion SPECT/CT Imaging

OBJECTIVE

The aim of this study was to investigate the relationship between patient characteristics and adenosine-related side-effects during stress myocard perfusion imaging (MPI). The effect of presence of adenosine-related side-effects on the diagnostic value of MPI with integrated SPECT/CT system for coronary artery disease (CAD), was also assessed in this study.

METHODS

Total of 281 patients (109 M, 172 F; mean age:62.6±10) who underwent standard adenosine stress protocol for MPI, were included in this study. All symptoms during adenosine infusion were scored according to the severity and duration. For the estimation of diagnostic value of adenosine MPI with integrated SPECT/CT system, coronary angiography (CAG) or clinical follow-up were used as gold standard.

RESULTS

Total of 173 patients (61.6%) experienced adenosine-related side-effects (group 1); flushing, dyspnea, and chest pain were the most common. Other 108 patients completed pharmacologic stress (PS) test without any side-effects (group 2). Test tolerability were similar in the patients with cardiovascular or airway disease to others, however dyspnea were observed significantly more common in patients with mild airway disease. Body mass index (BMI) ≥30 kg/m2 and age ≤45 years were independent predictors of side-effects. The diagnostic value of MPI was similar in both groups. Sensitivity of adenosine MPI SPECT/CT was calculated to be 86%, specificity was 94% and diagnostic accuracy was 92% for diagnosis of CAD.

CONCLUSION

Adenosine MPI is a feasible and well tolerated method in patients who are not suitable for exercise stress test as well as patients with cardiopulmonary disease. However age ≤45 years and BMI ≥30 kg/m2 are the positive predictors of adenosine-related side-effects, the diagnostic value of adenosine MPI SPECT/CT is not affected by the presence of adenosine related side-effects.