Impact of sex on the assessment of the microvascular resistance reserve.

BACKGROUND: The microvascular resistance reserve (MRR) is an innovative index to assess the vasodilatory capacity of the coronary circulation while accounting for the presence of concomitant epicardial disease. The MRR has shown to be a valuable diagnostic and prognostic tool in the general coronary artery disease (CAD) population. However, considering the fundamental aspects of its assessment and the unique hemodynamic characteristics of women, it is crucial to provide additional considerations for evaluating the MRR specifically in women. AIM: The aim of this study was to assess the diagnostic and prognostic applicability of the MRR in women and assess the potential differences across different sexes. METHODS: From the ILIAS Registry, we enrolled all patients with a stable indication for invasive coronary angiography, ensuring complete physiological and follow-up data. We analyzed the diagnostic value by comparing differences between sexes and evaluated the prognostic value of the MRR specifically in women, comparing it to that in men. RESULTS: A total of 1494 patients were included of which 26% were women. The correlation between MRR and CFR was good and similar between women (r = 0.80, p < 0.005) and men (r = 0.81, p < 0.005). The MRR was an independent and important predictor of MACE in both women (HR 0.67, 0.47-0.96, p = 0.027) and men (HR 0.84, 0.74-0.95, p = 0.007). The optimal cut-off value for MRR in women was 2.8 and 3.2 in men. An abnormal MRR similarly predicted MACE at 5-year follow-up in both women and men. CONCLUSION: The MRR seems to be equally applicable in both women and men with stable coronary artery disease.

Comparative assessment of coronary physiology using transthoracic pulsed-wave Doppler and myocardial contrast echocardiography in rats.

BACKGROUND: Coronary physiology assessment in rodents by ultrasound is an excellent noninvasive and easy to perform technique, including pulsed-wave Doppler (PWD) and myocardial contrast echocardiography (MCE). Both techniques and the corresponding calculated parameters were investigated in this study at rest as well as their response to pharmacologically induced stress. METHODS: Left ventricular myocardial function was assessed in eight anaesthetised rats using transthoracic echocardiography. Coronary physiology was assessed by both PWD of the left coronary artery and MCE using a bolus method. Measurements were performed at rest and under stimulation with adenosine and dobutamine. Effects of stimulation on the calculated parameters were evaluated and rated by effect size (η2). RESULTS: Changes could be demonstrated by selected parameters of PWD and MCE. The clearest effect in PWD was found for diastolic peak velocity (η2 = 0.58). It increased from 528 ± 110 mm/s (mean ± standard deviation) at rest to 839 ± 342 mm/s (p = 0.001) with adenosine and 1093 ± 302 mm/s with dobutamine (p = 0.001). The most distinct effect from MCE was found for the normalised wash-in rate (η2 = 0.58). It increased from 1.95 ± 0.35% at rest to 3.87 ± 0.85% with adenosine (p = 0.001) and 3.72 ± 1.03% with dobutamine (p = 0.001). CONCLUSION: Induced changes in coronary physiology by adenosine and dobutamine could successfully be monitored using MCE and PWD in anaesthetised rats. Due to the low invasiveness of the measurements, this protocol could be used for longitudinal animal studies.

Angiography-derived assessment of coronary microcirculatory resistance in patients with suspected myocardial ischaemia and non-obstructive coronary arteries.

BACKGROUND: Myocardial ischaemia with non-obstructive coronary arteries (INOCA) represents a challenging and frequent, but largely underdiagnosed, condition. AIMS: We aimed to investigate the feasibility and diagnostic value of angiography-derived coronary microcirculatory resistance in patients with INOCA syndrome. METHODS: This is an investigator-driven, prospective and blinded study. The diagnostic yield of angiography-derived index of coronary microcirculatory resistance (angio-IMR) was investigated against thermodilution-derived IMR (thermo-IMR) in patients with clinically indicated coronary angiography due to suspected myocardial ischaemia and angiographically normal or non-obstructive coronary arteries. The angio-IMR was derived from resting angiograms (contrast-flow angio-IMR [cAngio-IMR]) by an expert analyst blinded to the thermo-IMR. An independent, blinded, physiology core laboratory analysed the raw intracoronary physiology data and provided the final thermo-IMR values. RESULTS: A total of 104 patients (108 coronary vessels) were analysed after fulfilling predefined inclusion criteria. Most patients were female (67%). Obstructive epicardial disease was angiographically (percent diameter stenosis <50%) and physiologically (fractional flow reserve>0.80) ruled out in all cases. Median thermo-IMR and cAngio-IMR were 16.6 (12.7, 23.0) and 16.8 (12.8, 23.1) units, respectively (median difference -0.31, 95% confidence interval: -1.53 to 1.00; p=0.654). cAngio-IMR showed good correlation (Pearson coefficient 0.76; p<0.001), agreement (mean bias 0.4), discriminatory power (area under the curve from the receiver operator characteristics 0.865; p<0.001) and accuracy (85%), compared to thermo-IMR (≥25 U). CONCLUSIONS: Evaluating coronary microcirculatory resistance in patients with INOCA syndrome using cAngio-IMR is feasible and accurate. By circumventing the need of coronary instrumentation and hyperaemic drugs, this method may facilitate the assessment of coronary microcirculatory resistance in patients with suspected INOCA. CLINICALTRIALS: gov: NCT04827498.

Prognostic value of Doppler echocardiographic coronary flow velocity assessment at rest in elderly patients.

BACKGROUND: Atherosclerosis and coronary artery disease (CAD) are a common condition and cause of death in the elderly population. There are difficulties with risk assessment in the elderly as the objectification of their symptomatic status can be challenging due to neuromuscular weakness, physical deconditioning or neurological, orthopaedic, peripheral vascular, or respiratory limitations. Non-invasive coronary artery velocity assessment by Doppler method at rest could be helpful in the elderly population. To evaluate the prognostic role of coronary artery ultrasound assessment in a non-selected elderly population in everyday clinical practice. METHODS: One hundred forty-five patients, aged ≥75years (99 women; 80 ± 4 years), formed the study group. Left coronary artery flows were scanned in addition to conventional echocardiography. During a median follow-up of 26 months, 16 deaths and 2 non-fatal MI occurred. RESULTS: In multivariable analysis, maximal coronary velocity was the only independent predictor for mortality (heart rate [HR]: 1.02, 95%, CI: 1.01-1.04, p < .0005) and for mortality/MI (HR: 1.02, 95%, CI: 1.01-1.03, p < .0001). The value of 110 cm/s maximal coronary flow velocity (CFL) in the proximal segments of left arteries was the best predictor for death, sensitivity 50%, specificity 90%, p < .005. The annual mortality rate was 16.6% persons/year for patients with elevated CFL ≥110 cm/s. The value 81 cm/s was the best predictor for death/MI, sensitivity 61%, specificity 80%, p < .0005; annual mortality rate was 11.2% persons/year for patients with elevated CFL ≥81 cm/s (p < .0001). CONCLUSION: Doppler CFL scanning during routine echocardiography is a feasible and valuable tool for assessment of short-term prognosis in elderly patients.

Myocardial contrast echocardiography assessment of perfusion abnormalities in hypertrophic cardiomyopathy.

BACKGROUND: Perfusion defects during stress can occur in hypertrophic cardiomyopathy (HCM) from either structural or functional abnormalities of the coronary microcirculation. In this study, vasodilator stress myocardial contrast echocardiography (MCE) was used to quantify and spatially characterize hyperemic myocardial blood flow (MBF) deficits in HCM. METHODS: Regadenoson stress MCE was performed in patients with septal-variant HCM (n = 17) and healthy control subjects (n = 15). The presence and spatial distribution (transmural diffuse, patchy, subendocardial) of perfusion defects was determined by semiquantitative analysis. Kinetic analysis of time-intensity data was used to quantify MBF, microvascular flux rate (ß), and microvascular blood volume. In patients undergoing septal myectomy (n = 3), MCE was repeated > 1 years after surgery.  RESULTS: In HCM subjects, perfusion defects during stress occurred in the septum in 80%, and in non-hypertrophied regions in 40%. The majority of septal defects (83%) were patchy or subendocardial, while 67% of non-hypertrophied defects were transmural and diffuse. On quantitative analysis, hyperemic MBF was approximately 50% lower (p < 0.001) in the hypertrophied and non-hypertrophied regions of those with HCM compared to controls, largely based on an inability to augment ß, although hypertrophic regions also had blood volume deficits. There was no correlation between hyperemic MBF and either percent fibrosis on magnetic resonance imaging or outflow gradient, yet those with higher degrees of fibrosis (≥ 5%) or severe gradients all had low septal MBF during regadenoson. Substantial improvement in hyperemic MBF was observed in two of the three subjects undergoing myectomy, both of whom had severe pre-surgical outflow gradients at rest. CONCLUSION: Perfusion defects on vasodilator MCE are common in HCM, particularly in those with extensive fibrosis, but have a different spatial pattern for the hypertrophied and non-hypertrophied segments, likely reflecting different contributions of functional and structural abnormalities. Improvement in hyperemic perfusion is possible in those undergoing septal myectomy to relieve obstruction.  TRIAL REGISTRATION: ClinicalTrials.gov NCT02560467.

Angiography derived assessment of the coronary microcirculation: is it ready for prime time?

INTRODUCTION: Non-obstructive coronary arteries (NOCA) are present in 39.7% to 62.4% of patients who undergo elective angiography. Coronary microcirculation (<400 µm) is not visible on angiography therefore functional assessment, invasive or noninvasive plays a prior role to help provide a more personalized diagnosis of angina. AREA COVERED: In this review, we revisit the pathophysiology, clinical importance, and invasive assessment of the coronary microcirculation, and discuss angiography-derived indices of microvascular resistance. A comprehensive literature review over four decades is also undertaken. EXPERT OPINION: The coronary microvasculature plays an important role in flow autoregulation and metabolic regulation. Invasive assessment of microvascular resistance is a validated modality with independent prognostic value, nevertheless, its routine application is hampered by the requirement of intravascular instrumentation and hyperemic agents. The angiography-derived index of microvascular resistance has emerged as a promising surrogate in pilot studies, however, more data are needed to validate and compare the diagnostic and prognostic accuracy of different equations as well as to illustrate the relationship between angiography-derived parameters for epicardial coronary arteries and those for the microvasculature.

Assessment of the Relationship Between the Adropin Levels and the Coronary Collateral Circulation in Patients with Chronic Coronary Syndrome. / Avaliação da Relação entre Níveis de Adropina e Circulação Colateral Coronária em Pacientes com Síndrome Coronariana Crônica.

BACKGROUND: Coronary collateral circulation (CCC) provides an alternative blood flow to myocardial tissue exposed to ischemia and helps to preserve myocardial functions. Endothelial-derived nitric-oxide (NO) production and vascular endothelial growth factor (VEGF) have been suggested as the most important factors in the development of CCC. Adropin is a peptide hormone responsible for energy hemostasis, and is known for its positive effects on the endothelium through NO and VEGF. OBJECTIVE: The aim of this study is to investigate the association between adropin and the presence of CCC in patients with chronic coronary syndrome (CCS). METHODS: A total of 102 patients with CCS, who had complete occlusion of at least one major epicardial coronary artery, were included in the study and were divided into two groups: the group of patients (n:50) with poor CCC (Rentrop 0-1) and the group of patients (n:52) with good CCC (Rentrop 2-3). The level of significance adopted in the statistical analysis was 5%. RESULTS: Mean adropine levels were found as 210.83±17.76 pg/mL and 268.25±28.94 pg/mL in the poor and good CCC groups, respectively (p<0.001). Adropin levels proved to be positively correlated with neutrophil-to-lymphocyte ratios (r:0.17, p:0.04) and the rentrop scores (r:0.76, p<0.001), and negatively correlated with age (r:-0.23, p:0.01) and Gensini scores (r:-0.19, p:0.02). Adropin level is a strong independent predictor of good CCC development (OR:1.12, 95% CI:(1.06-1.18), p<0.001). CONCLUSION: This study suggests that adropin levels may be a possible factor associated with the presence of CCC in CCS patients.

FUNDAMENTO: A circulação colateral coronária (CCC) proporciona um fluxo sanguíneo alternativo a tecido miocárdico exposto a isquemia e ajuda a preservar as funções miocárdicas. A produção endotelial de óxido nítrico (NO) e o fator de crescimento endotelial vascular (VEGF) foram apontados como os fatores mais importantes no desenvolvimento da CCC. A adropina é um hormônio peptídeo responsável pela hemostasia energética, e é conhecida por seus efeitos positivos no endotélio por NO e VEGF. OBJETIVO: O objetivo deste estudo é investigar a associação entre adropina e a presença de CCC em pacientes com síndrome coronariana crônica (SCC). MÉTODOS: Um total de 102 pacientes com SCC, que tinham oclusão total de pelo menos 1 artéria coronária epicárdica importante, foram incluídos no estudo e foram divididos em dois grupos: o grupo de pacientes (n: 50) com CCC ruim (Rentrop 0-1) e o grupo de pacientes (n: 52) com CCC boa (Rentrop 2-3). O nível de significância adotado para a análise estatística foi 5%. RESULTADOS: Os níveis médios de adropina identificados foram 210,83±17,76 pg/mL e 268,25±28,94 pg/mL nos grupos com CCC ruim e boa, respectivamente (p<0,001). Detectou-se que os níveis de adropina têm correlação com as razões neutrófilo-linfócito (r: 0,17, p: 0,04) e com os escores de Rentrop (r: 0,76, p<0,001), e correlação negativa com idade (r: -0,23, p: 0,01) e com os escores Gensini (r: -0,19, p: 0,02). O nível de adropina é um preditor independente da boa evolução da CCC (RC: 1.12, IC 95%: (1,06­1,18), p<0,001). CONCLUSÃO: Este estudo sugere que os níveis de adropina podem ser um fator associado à de CCC em pacientes com SCC.

Commentary on the enigma of small vessel disease in hypertrophic cardiomyopathy: is invasive assessment of microvascular resistance a novel independent predictor of prognosis?

The key pathophysiological features in hypertrophic cardiomyopathy are ventricular hypertrophy, diastolic dysfunction, and abnormalities in the mitral valve apparatus, but coronary microvascular dysfunction and ischemia have also been described. The small vessel disease changes could be reflected in the invasive measurement of the index of microvascular resistance, with prognostic potential.

Phasic flow patterns of right versus left coronary arteries in patients undergoing clinical physiological assessment.

BACKGROUND: Coronary blood flow in humans is known to be predominantly diastolic. Small studies in animals and humans suggest that this is less pronounced or even reversed in the right coronary artery (RCA). AIMS: This study aimed to characterise the phasic patterns of coronary flow in the left versus right coronary arteries of patients undergoing invasive physiological assessment. METHODS: We analysed data from the Iberian-Dutch-English Collaborators (IDEAL) study. A total of 482 simultaneous pressure and flow measurements from 301 patients were included in our analysis. RESULTS: On average, coronary flow was higher in diastole both at rest and during hyperaemia in both the RCA and LCA (mean diastolic-to-systolic velocity ratio [DSVR] was, respectively, 1.85±0.70, 1.76±0.58, 1.53±0.34 and 1.58±0.43 for LCArest, LCAhyp, RCArest and RCAhyp, p<0.001 for between-vessel comparisons). Although the type of RCA dominance affected the DSVR magnitude (RCAdom=1.55±0.35, RCAco-dom=1.40±0.27, RCAnon-dom=1.35; standard deviation not reported as n=3), systolic flow was very rarely predominant (DSVR was greater than or equal to 1.00 in 472/482 cases [97.9%] overall), with equal prevalence in the LCA. Stenosis severity or microvascular dysfunction had a negligible impact on DSVR in both the RCA and LCA (DSVR x hyperaemic stenosis resistance R2 =0.018, p=0.03 and DSVR x coronary flow reserve R2 <0.001, p=0.98). CONCLUSIONS: In patients with coronary artery disease undergoing physiological assessment, diastolic flow predominance is seen in both left and right coronary arteries. Clinical interpretation of coronary physiological data should therefore not differ between the left and the right coronary systems.

Accurate assessment of coronary blood flow by continuous thermodilution technique: Validation in a swine model.

OBJECTIVE: To assess the accuracy of coronary thermodilution measurements made with the RayFlow® infusion catheter. BACKGROUND: Measurements of absolute coronary blood flow (ABF) and absolute microvascular resistance (Rµ ) by continuous coronary thermodilution can be obtained in humans but their accuracy using a novel dedicated infusion catheter has not yet been validated. We compared ABF values obtained at different infusion rates to coronary blood flow (CBF) values obtained using flow probes, in swine. METHODS: Twelve domestic swine were instrumented with coronary flow probes placed around the left anterior descending and circumflex coronary arteries. ABF was assessed with the RayFlow® infusion catheter during continuous saline infusion at fixed rates of 5 (n = 14), 10 (n = 15), 15 (n = 19), and 20 (n = 12) ml/min. RESULTS: In the 60 measurements, ABF measured using thermodilution averaged 41 ± 17 ml/min (range from 17 to 90) and CBF values obtained with the coronary flow probes averaged 37 ± 18 ml/min (range from 8 to 87). The corresponding Rµ values were 1532 ± 791 (range from 323 to 5103) and 1903 ± 1162 (range from 287 to 6000) Woods units using thermodilution and coronary flow probe assessments, respectively. ABF and Rµ values measured using thermodilution were significantly correlated with the corresponding measurements obtained using coronary flow probes (R = 0.84 [0.73-0.95] and R = 0.80 [0.69-0.88], respectively). CONCLUSIONS: ABF and Rµ assessed by continuous saline infusion through a RayFlow® catheter closely correlate with measurements obtained with the gold standard coronary flow probes in a swine model.

Myocardial Bridging: Diagnosis, Functional Assessment, and Management: JACC State-of-the-Art Review.

Myocardial bridging (MB) is a congenital coronary anomaly in which a segment of the epicardial coronary artery traverses through the myocardium for a portion of its length. The muscle overlying the artery is termed a myocardial bridge, and the intramyocardial segment is referred to as a tunneled artery. MB can occur in any coronary artery, although is most commonly seen in the left anterior descending artery. Although traditionally considered benign in nature, increasing attention is being given to specific subsets of MB associated with ischemic symptomatology. The advent of contemporary functional and anatomic imaging modalities, both invasive and noninvasive, have dramatically improved our understanding of dynamic pathophysiology associated with MBs. This review provides a contemporary overview of epidemiology, pathobiology, diagnosis, functional assessment, and management of MBs.

Simplified Assessment of the Index of Microvascular Resistance.

BACKGROUND: To validate a simplified invasive method for the calculation of the index of microvascular resistance (IMR). METHODS: This is a prospective, single-center study of patients with chronic coronary syndromes presenting with nonobstructive coronary artery disease. IMR was obtained using both intravenous (IV) adenosine and intracoronary (IC) papaverine. Each IMR measurement was obtained in duplicate. The primary objective was the agreement between IMR acquired using adenosine and papaverine. Secondary objectives include reproducibility of IMR and time required for the IMR measurement. RESULTS: One hundred and sixteen IMR measurements were performed in 29 patients. The mean age was 68.8 ± 7.24 years, and 27.6% was diabetics. IMR values were similar between papaverine and adenosine (17.7 ± 7.26 and 20.1 ± 8.6, p=0.25; Passing-Bablok coefficient A 0.58, 95% CI -2.42 to 3.53; coefficient B 0.90, 95% CI -0.74 to 1.07). The reproducibility of IMR was excellent with both adenosine and papaverine (ICC 0.78, 95% CI 0.63 to 0.88 and ICC 0.93, 95% CI 0.87 to 0.97). The time needed for microvascular assessment was significantly shortened by the use of IC papaverine (3.23 (2.84, 3.78) mins vs. 5.48 (4.94, 7.09) mins, p < 0.0001). CONCLUSION: IMR can be reliably measured using IC papaverine with similar results compared to intravenous infusion of adenosine with increased reproducibility and reduced procedural time. This approach simplifies the invasive assessment of the coronary microcirculation in the catheterization laboratory.

Impact of coronary artery disease on contractile function and ventricular-arterial coupling during exercise: Simultaneous assessment of left-ventricular pressure-volume and coronary pressure and flow during cardiac catheterization.

Coronary artery disease (CAD) can adversely affect left ventricular (LV) performance during exercise by impairment of contractile function in the presence of increasing afterload. By performing invasive measures of LV pressure-volume and coronary pressure and flow during exercise, we sought to accurately measure this with comparison to the control group. Sixteen patients, with CCS class >II angina and CAD underwent invasive simultaneous measurement of left ventricular pressure-volume and coronary pressure and flow velocity during cardiac catheterization. Measurements performed at rest were compared with peak exercise using bicycle ergometry. The LV contractile function was measured invasively using the end-systolic pressure-volume relationship, a load independent marker of contractile function (Ees). Vascular afterload forces were derived from the ratio of LV end-systolic pressure to stroke volume to generate arterial elastance (Ea). These were combined to assess cardiovascular performance (ventricular-arterial [VA] coupling ratio [Ea/Ees]). Eleven patients demonstrated flow-limiting (FL) CAD (hyperemic Pd/Pa <0.80; ST-segment depression on exercise); five patients without flow-limiting (NFL) CAD served as the control group. Exercise in the presence of FL CAD was associated impairment of Ees, increased Ea, and deterioration of VA coupling. In the control cohort, exercise was associated with increased Ees and improved VA coupling. The backward compression wave energy directly correlated with the magnitude contraction as measured by dP/dTmax (r = 0.88, p = 0.004). This study demonstrates that in the presence of flow-limiting CAD, exercise to maximal effort can lead to impairment of LV contractile function and a deterioration in VA coupling compared to a control cohort.

Non-invasive assessment of temporal changes in myocardial microvascular function in persons with type 2 diabetes and healthy controls.

BACKGROUND: Cardiac Rubidium-82 (82 Rb) positron emission tomography/computed tomography (PET/CT) provides a measure of the myocardial blood flow and the myocardial flow reserve, which reflects the function of both large epicardial arteries and the myocardial microcirculation. Knowledge on changes in the myocardial microvascular function over time is lacking. METHODS: In this cohort study, we recruited 60 persons with type 2 diabetes and 30 non-diabetic controls, in 2013; all free of overt cardiovascular disease. All underwent a cardiac 82 Rb PET/CT scan. In 2019, all survivors (n = 82) were invited for a repeated cardiac 82 Rb PET/CT scan using the same protocol, and 29 with type 2 diabetes and 19 controls participated. RESULTS: Median duration between visits was 6.2 years (IQR: 6.1-6.3). In the total cohort, the mean age was 66.4 years (SD: 9.3) and 33% were females. The myocardial flow reserve was lower in persons with type 2 diabetes compared to controls (p = 0.002) but there was no temporal change in the myocardial flow reserve in participants with type 2 diabetes: mean change: -0.22 (95% CI: -0.47 to 0.02) nor in controls: -0.12 (-0.49 to 0.25) or when comparing type 2 diabetes to controls: mean difference: -0.10 (95% CI: -0.52 to 0.31). The temporal reduction in stress-induced myocardial blood flow did not differ within the groups but was more pronounced in type 2 diabetes compared to controls: mean difference: -0.30 (95% CI: -0.55 to -0.04). CONCLUSION: The myocardial microvascular function was impaired in persons with type 2 diabetes compared to controls but did not change significantly in either of the groups when evaluated over 6 years.

Role of quantitative myocardial blood flow and 13N-ammonia washout for viability assessment in ischemic cardiomyopathy.

OBJECTIVE: Positron emission tomography (PET) integrating assessment of perfusion with 13N-ammonia (NH3) and viability with 18F-fluorodeoxyglucose (FDG) has high accuracy to identify viable, hibernating myocardium. We tested whether quantification of myocardial blood flow (MBF) and washout (k2) can predict myocardial viability using FDG as standard of reference. METHODS: In 180 consecutive patients with ischemic cardiomyopathy, myocardium was categorized on a segment-level into normal, ischemic, hibernating, and scar. From dynamic images, stress MBF, rest MBF, and k2 were derived and myocardial flow reserve (MFR) and volume of distribution (VD) were calculated. RESULTS: Across myocardial tissues, all parameters differed significantly. The area under the curve (AUC) was 0.564 (95% CI 0.527-0.601), 0.635 (0.599-0.671), 0.553 (0.516-0.591), 0.520 (0.482-0.559), and 0.560 (0.522-0.597) for stress MBF, rest MBF, MFR, k2, and VD. The generalized linear mixed model correctly classified 81% of scar as viable, hibernating myocardium. If the threshold of rest MBF to predict viability was set to 0.45 mL·min-1·g-1, sensitivity and specificity were 96% and 12%, respectively. CONCLUSION: Quantitative NH3 PET parameters have low to moderate diagnostic performance to predict viability in ischemic cardiomyopathy. However, if rest MBF falls below 0.45 mL·min-1·g-1, viability testing by FDG-PET may be safely deferred.

Assessment of motion correction in dynamic rubidium-82 cardiac PET with and without frame-by-frame adjustment of attenuation maps for calculation of myocardial blood flow.

BACKGROUND: Patient motion during pharmacological stressing can have substantial impact on myocardial blood flow (MBF) estimated from dynamic PET. This work evaluated a motion correction algorithm with and without adjustment of the PET attenuation map. METHODS: Frame-by-frame motion correction was performed by three users on 30 rubidium-82 studies. Data were divided equally into three groups of motion severity [mild (M1), moderate (M2) and severe (M3)]. MBF data were compared for non-motion corrected (NC), motion-corrected-only (MC) and with adjustment of the attenuation map (MCAC). Percentage differences of MBF were calculated in the coronary territories and 17-segment polar plots. Polar plots of spill-over were also generated from the data. RESULTS: Median differences of 23% were seen in the RCA and 18% for the LAD in the M3 category for MC vs NC images. Differences for MCAC vs MC images were considerably smaller and typically < 10%. Spill-over plots for MC and MCAC were notably more uniform compared with NC images. CONCLUSION: Motion correction for dynamic rubidium data is desirable for future MBF software updates. Adjustment of the PET attenuation map results in only marginal differences and therefore is unlikely to be an essential requirement. Assessing the uniformity of spill-over plots is a useful visual aid for verifying motion correction techniques.

Diagnostic value of the novel CMR parameter "myocardial transit-time" (MyoTT) for the assessment of microvascular changes in cardiac amyloidosis and hypertrophic cardiomyopathy.

BACKGROUND: Coronary microvascular dysfunction (CMD) is present in various non-ischemic cardiomyopathies and in particular in those with left-ventricular hypertrophy. This study evaluated the diagnostic value of the novel cardiovascular magnetic resonance (CMR) parameter "myocardial transit-time" (MyoTT) in distinguishing cardiac amyloidosis from other hypertrophic cardiomyopathies. METHODS: N = 20 patients with biopsy-proven cardiac amyloidosis (CA), N = 20 patients with known hypertrophic cardiomyopathy (HCM), and N = 20 control patients without relevant cardiac disease underwent dedicated CMR studies on a 1.5-T MR scanner. The CMR protocol comprised cine and late-gadolinium-enhancement (LGE) imaging as well as first-pass perfusion acquisitions at rest for MyoTT measurement. MyoTT was defined as the blood circulation time from the orifice of the coronary arteries to the pooling in the coronary sinus (CS) reflecting the transit-time of gadolinium in the myocardial microvasculature. RESULTS: MyoTT was significantly prolonged in patients with CA compared to both groups: 14.8 ± 4.1 s in CA vs. 12.2 ± 2.5 s in HCM (p = 0.043) vs. 7.2 ± 2.6 s in controls (p < 0.001). Native T1 and extracellular volume (ECV) were significantly higher in CA compared to HCM and controls (p < 0.001). Both parameters were associated with a higher diagnostic accuracy in predicting the presence of CA compared to MyoTT: area under the curve (AUC) for native T1 = 0.93 (95% confidence interval (CI) = 0.83-1.00; p < 0.001) and AUC for ECV = 0.95 (95% CI = 0.88-1.00; p < 0.001)-compared to the AUC for MyoTT = 0.76 (95% CI = 0.60-0.92; p = 0.008). In contrast, MyoTT performed better than all other CMR parameters in differentiating HCM from controls (AUC for MyoTT = 0.93; 95% CI = 0.81-1.00; p = 0.003 vs. AUC for native T1 = 0.69; 95% CI = 0.44-0.93; p = 0.20 vs. AUC for ECV = 0.85; 95% CI = 0.66-1.00; p = 0.017). CONCLUSION: The relative severity of CMD (measured by MyoTT) in relationship to extracellular changes (measured by native T1 and/or ECV) is more pronounced in HCM compared to CA-in spite of a higher absolute MyoTT value in CA patients. Hence, MyoTT may improve our understanding of the interplay between extracellular/intracellular and intravasal changes that occur in the myocardium during the disease course of different cardiomyopathies.