Novel implementation of cardiac magnetic resonance first-pass perfusion imaging for semi-quantitatively evaluating microvascular dysfunction in paediatric patients with Duchenne muscular dystrophy

OBJECTIVES

The current study aimed to assess myocardial microcirculation dysfunction via cardiac magnetic resonance (CMR) first-pass perfusion imaging in children with Duchenne muscular dystrophy (DMD).

METHODS

In total, 67 children with DMD and 15 controls who underwent contrast-enhanced CMR first-pass perfusion imaging were enrolled in this study. CMR first-pass perfusion and late gadolinium enhancement (LGE) sequences were acquired. Further, the global, regional, and coronary artery distribution area perfusion indexes (PI), upslope (%BL), maximum signal intensity (MaxSI), time to maximum signal intensity (TTM), and baseline SI were analysed. The perfusion parameters of the LGE positive (+), LGE negative (-), and control groups were compared. Pearson correlation analysis was performed to assess the association between myocardial microcirculation and conventional cardiac function and LGE parameters.

RESULTS

The LGE+ group had a significantly lower global and apical-ventricular MaxSI than the control group (all P < .05). The left anterior descending arterial (LAD), left circumflex coronary arterial (LCX), and right coronary arterial (RCA) segments of the LGE+ group had a lower upslope and MaxSI than those of the control group (all P < .05). The LAD segments of the LGE- group had a lower MaxSI than those of the control group (41.10 ± 11.08 vs 46.36 ± 13.04; P < .001). The LCX segments of the LGE- group had a lower PI and upslope than those of the control group (11.05 ± 2.84 vs 12.46 ± 2.82; P = .001; 59.31 ± 26.76 vs 68.57 ± 29.99; P = .002). Based on the correlation analysis, the upslope, MaxSI, and TTM were correlated with conventional cardiac function and LGE extent.

CONCLUSIONS

Paediatric patients with DMD may present with microvascular dysfunction. This condition may appear before LGE and may be correlated with coronary artery blood supply and LGE extent.

ADVANCES IN KNOWLEDGE

First-pass perfusion parameters may reveal the status of myocardial microcirculation and reflect the degree of myocardial injury at an earlier time in DMD patients. Perfusion parameters should be analysed not only via global or base, middle, and apical segments but also according to coronary artery distribution area, which may detect myocardial microvascular dysfunction at an earlier stage, in DMD patients with LGE-.

Prediction Model for Contractile Function of Circulatory Death Donor Hearts Based on Microvascular Flow Shifts During Ex Situ Hypothermic Cardioplegic Machine Perfusion

Background Hearts procured from circulatory death donors (DCD) are predominantly maintained by machine perfusion (MP) with normothermic donor blood. Currently, DCD heart function is evaluated by lactate and visual inspection. We have shown that MP with the cardioplegic, crystalloid Custodiol-N solution is superior to blood perfusion to maintain porcine DCD hearts. However, no method has been developed yet to predict the contractility of DCD hearts after cardioplegic MP. We hypothesize that the shift of microvascular flow during continuous MP with a cardioplegic preservation solution predicts the contractility of DCD hearts. Methods and Results In a pig model, DCD hearts were harvested and maintained by MP with hypothermic, oxygenated Custodiol-N for 4 hours while myocardial microvascular flow was measured by Laser Doppler Flow (LDF) technology. Subsequently, hearts were perfused with blood for 2 hours, and left ventricular contractility was measured after 30 and 120 minutes. Various novel parameters which represent the LDF shift were computed. We used 2 combined LDF shift parameters to identify bivariate prediction models. Using the new prediction models based on LDF shifts, highest r² for end-systolic pressure was 0.77 (P=0.027), for maximal slope of pressure increment was 0.73 (P=0.037), and for maximal slope of pressure decrement was 0.75 (P=0.032) after 30 minutes of reperfusion. After 120 minutes of reperfusion, highest r² for end-systolic pressure was 0.81 (P=0.016), for maximal slope of pressure increment was 0.90 (P=0.004), and for maximal slope of pressure decrement was 0.58 (P=0.115). Identical prediction models were identified for maximal slope of pressure increment and for maximal slope of pressure decrement at both time points. Lactate remained constant and therefore was unsuitable for prediction. Conclusions Contractility of DCD hearts after continuous MP with a cardioplegic preservation solution can be predicted by the shift of LDF during MP.

Impact of Type 2 Diabetes Mellitus on Epicardial Adipose Tissue and Myocardial Microcirculation by MRI in Postmenopausal Women

BACKGROUND

Type 2 diabetes mellitus (T2DM) often occurs conjunctly with the menopausal transition in female patients. In addition, epicardial adipose tissue (EAT) has an unfavorable impact on the myocardium and coronary arteries under the influence of metabolic disorders.

PURPOSE

To investigate the impact of T2DM on EAT and myocardial microvascular function in postmenopausal women.

STUDY TYPE

Retrospective.

POPULATION

One-hundred sixty-one postmenopausal women divided into three groups: newly diagnosed (≤5 years) T2DM (n = 56, 58.6 ± 7.7 years), long-term (>5 years) T2DM (n = 57, 61.9 ± 7.9 years), and healthy controls (n = 48, 59.4 ± 7.4 years).

FIELD STRENGTH/SEQUENCE

3.0 T; balanced steady-state free precession and inversion recovery prepared echo-planar sequences.

ASSESSMENT

EAT volume was quantified by delineating the epicardial border and the visceral layer of pericardium on the short-axis cine stacks. Perfusion parameters including upslope, maximum signal intensity (MaxSI) and time to maximum signal intensity (TTM) were derived from the first-pass perfusion signal intensity-time curves.

STATISTICAL TESTS

One-way analysis of variance, Pearson's and Spearman correlation, and multivariable linear regression. Two-sided P < 0.05 was considered statistically significant.

RESULTS

EAT volume was significantly increased in diabetic postmenopausal women compared to the controls (48.4 ± 13.4 mL/m² [newly diagnosed T2DM] vs. 58.4 ± 17.3 mL/m² [long-term T2DM] vs. 35.8 ± 12.3 mL/m² [controls]). Regarding perfusion parameters, upslope and MaxSI were significantly reduced (2.6 ± 1.0 [newly diagnosed T2DM] vs. 2.1 ± 0.8 [long-term T2DM] vs. 3.6 ± 1.3 [controls]; and 21.4 ± 6.9 [newly diagnosed T2DM] vs. 18.7 ± 6.4 [long-term T2DM] vs. 28.4 ± 8.6 [controls]), whereas TTM was significantly increased in the T2DM groups compared to the control group (23.6 ± 8.7 [newly diagnosed T2DM] vs. 27.1 ± 9.4 [long-term T2DM] vs. 21.4 ± 6.0 [controls]). Multivariable analysis (adjusted coefficient of determination [R² ] = 0.489) showed that EAT volume (β = -0.610) and menopausal age (β = 0.433) were independently correlated with decreased perfusion upslope.

DATA CONCLUSION

Diabetic postmenopausal women had significantly higher EAT volume and more impaired microcirculation compared to the controls. Increased EAT volume and earlier menopausal age were independently associated with microvascular dysfunction in these patients.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY STAGE: 3.

In Vivo Validation of a Novel Computational Approach to Assess Microcirculatory Resistance Based on a Single Angiographic View

(1) Background: In spite of the undeniable clinical value of the index of microvascular resistance (IMR) in assessing the status of coronary microcirculation, its use globally remains very low. The aim of this study was to validate the novel single-view, pressure-wire- and adenosine-free angiographic microvascular resistance (AMR) index, having the invasive wire-based IMR as a reference standard. (2) Methods: one hundred and sixty-three patients (257 vessels) were investigated with pressure wire-based IMR. Microvascular dysfunction (CMD) was defined by IMR ≥ 25. AMR was independently computed from the diagnostic coronary angiography in a blinded fashion. (3) Results: AMR demonstrated a good correlation (r = 0.83, p < 0.001) and diagnostic performance (AUC 0.94; 95% CI: 0.91 to 0.97) compared with wire-based IMR. The best cutoff value for AMR in determining IMR ≥ 25 was 2.5 mmHg*s/cm. The overall diagnostic accuracy of AMR was 87.2% (95% CI: 83.0% to 91.3%), with a sensitivity of 93.5% (95% CI: 87.0% to 97.3%), a specificity of 82.7% (95% CI: 75.6% to 88.4%), a positive predictive value of 79.4% (95% CI: 71.2% to 86.1%) and a negative predictive value of 94.7% (95% CI: 89.3% to 97.8%). No difference in terms of CMD rate was described among different clinical presentations. (4) Conclusions: AMR derived solely from a single angiographic view is a feasible computational alternative to pressure wire-based IMR, with good diagnostic accuracy in assessing CMD.

Myocardium microcirculation study in a healthy Chinese population using 3.0-T cardiac magnetic resonance intravoxel incoherent motion imaging

BACKGROUND

Intravoxel incoherent motion imaging (IVIM) can non-invasively evaluate diffusion and microvascular perfusion.

PURPOSE

To explore the myocardium microcirculation of a healthy Chinese population by using cardiac magnetic resonance (CMR) IVIM.

MATERIAL AND METHODS

A total of 80 healthy volunteers (44 men, 36 women) who underwent 3.0-T CMR examination were enrolled. All participants had cardiac cine imaging and short-axis CMR-IVIM of the left ventricle (LV) using multiple b-values. The consistency of the IVIM parameters was assessed by intraclass correlation coefficient (ICC) and the Bland-Altman test. Spearman correlation analysis was performed between IVIM parameters and age, and body mass index (BMI). The differences of IVIM parameters were analyzed between gender and different ages.

RESULTS

LV end-diastolic volume (EDV), end-systolic volume (ESV), LVmass, cardiac output (CO), and BMI in the male group were higher than those in the female group (P<0.05). IVIM parameters had good intra-observer and inter-observer consistency (≥0.75). Bland-Altman analysis also showed good intra-observer and inter-observer consistency. ADC_fast decreased with increasing female age (rs = -0.37; P = 0.01), while IVIM parameters had no correlation with BMI regardless of sex. ADC_fast in the female group had a statistical difference between different age groups. The ADC_slow and f in the male group were lower than those in the female group (P<0.05); however, there was no statistical difference in ADC_fast between genders.

CONCLUSION

IVIM parameters in healthy Chinese volunteers provided good consistency. There was a negative correlation between ADC_fast and age in the female group.

Relationship of Laser-Doppler-Flow and coronary perfusion and a concise update on the importance of coronary microcirculation in donor heart machine perfusion

BACKGROUND

Machine perfusion (MP) is a novel method for donor heart preservation. The coronary microvascular function is important for the transplantation outcome. However, current research on MP in heart transplantation focuses mainly on contractile function.

OBJECTIVE

We aim to present the application of Laser-Doppler-Flowmetry to investigate coronary microvascular function during MP. Furthermore, we will discuss the importance of microcirculation monitoring for perfusion-associated studies in HTx research.

METHODS

Porcine hearts were cardioplegically arrested and harvested (Control group, N = 4). In an ischemia group (N = 5), we induced global ischemia of the animal by the termination of mechanical ventilation before harvesting. All hearts were mounted on an MP system for blood perfusion. After 90 minutes, we evaluated the effect of coronary perfusion pressures from 20 to 100 mmHg while coronary laser-doppler-flow (LDF) was measured.

RESULTS

Ischemic hearts showed a significantly decreased relative LDF compared to control hearts (1.07±0.06 vs. 1.47±0.15; p = 0.034). In the control group, the coronary flow was significantly lower at 100 mmHg of perfusion pressure than in the ischemia group (895±66 ml vs. 1112±32 ml; p = 0.016).

CONCLUSIONS

Laser-Doppler-Flowmetry is able to reveal coronary microvascular dysfunction during machine perfusion of hearts and is therefore of substantial interest for perfusion-associated research in heart transplantation.

Monitoring of perfusion quality and prediction of donor heart function during ex-vivo machine perfusion by myocardial microcirculation versus surrogate parameters

Currently, lactate (Lac) is used to evaluate machine perfusion (MP) of hearts, donated after circulatory death (DCD). We hypothesize that monitoring of myocardial microcirculation (mLDP) by Laser-Doppler-Perfusion is superior to Lac to evaluate perfusion and predict contractility. In a pig model, DCD-hearts were perfused 4 hours followed by reperfusion and left ventricular contractility measurement. Lac and mLDP were measured every 30 min in successfully (N = 9) and unsuccessfully (N = 7) maintained hearts. Successfully maintained hearts showed decreasing Lac (5.6 to 2.8 mmol/L) and slightly downregulated (92%) mLDP. In unsuccessfully maintained hearts Lac first decreased (5.1 to 3.8 mmol/L) followed by increase and mLDP dropped to 39%. In a single-variable regression only mLDP showed a significant r² for systolic (0.514, p = 0.045) and diastolic (0.501, p = 0.049) parameters. The combination of mLDP and Lac (r² = 0.876, p = 0.005) showed best results. mLDP seems to be superior to Lac to show perfusion disorders and predict DCD-heart contractility.

Invasive Assessment of the Myocardial Microcirculation during Beating Heart Coronary Artery Bypass Grafting

Coronary artery bypass grafting may be associated with several cardiac complications, including ischemia, acute myocardial infarction, arrhythmias, or hemodynamic instability. Accumulating evidence suggests that well-developed coronary collateral circulation may protect against adverse effects, including myocardial ischemia. Assessment of myocardial microvascular perfusion is, therefore, of great clinical interest in beating heart surgery. In this paper, myocardial microvascular perfusion is continuously assessed on the beating heart using laser Doppler flowmetry in consecutive patients who underwent coronary artery bypass grafting procedures. No significant (p = 0.110) differences were found between the averaged perfusion signal (n = 42) at the baseline, during artery occlusion, or after reperfusion (732.4 ± 148.0 vs. 711.4 ± 144.1 vs. 737.0 ± 141.2, respectively). In contrast, significantly different (p < 0.001) mean perfusion signals (n = 12) were found (805.4 ± 200.1 vs. 577.2 ± 212.8 vs. 649.3 ± 220.8) in a subset of patients who presented with hemodynamic instability and myocardial ischemia. Additionally, a strong positive correlation between the plasma levels of high-sensitivity troponin I and perfusion decrease level after artery occlusion was found (r = 0.854, p < 0.001). This study argues that myocardial microvascular perfusion remains constant during coronary artery bypass grafting on the beating heart in advanced coronary artery disease. This phenomenon is most likely due to an extensive coronary collateral circulation.

Cardiac microvascular rarefaction in hyperthyroidism-induced left ventricle dysfunction

OBJECTIVE

The pathophysiology underlying hyperthyroidism-induced left ventricle (LV) dysfunction and hypertrophy directly involves the heart and indirectly involves the neuroendocrine systems. The effects of hyperthyroidism on the microcirculation are still controversial in experimental models. We investigated the effects of hyperthyroidism on the cardiac function and microcirculation of an experimental rat model.

METHODS

Male Wistar rats (170-250 g) were divided into two groups: the euthyroid group (n = 10), which was treated with 0.9% saline solution, and the hyperthyroid group (n = 10), which was treated with l-thyroxine (600 μg/kg/day, i.p.) during 14 days. An echocardiographic study was performed to evaluate the alterations in cardiac function, structure and geometry. The structural capillary density and the expression of angiotensin II AT1 receptor in the LV were analyzed using histochemistry and immunohistochemistry, respectively.

RESULTS

Hyperthyroidism was found to induce profound cardiovascular alterations, such as systolic hypertension, tachycardia, LV dysfunction, cardiac hypertrophy, and myocardial fibrosis. This study demonstrates the existence of structural capillary rarefaction and the down-regulation of the cardiac angiotensin II AT1 receptor in the myocardium of hyperthyroid rats in comparison with euthyroid rats.

CONCLUSIONS

Microvascular rarefaction may be involved in the pathophysiology of hyperthyroidism-induced cardiovascular alterations.