Numerical Analysis on A Non-Critical Stenosis in Renal Artery

The increase in cardiovascular diseases worldwide has resulted in higher death rate of people globally; the primary reason being atherosclerosis. A better understanding of this condition can be achieved through the application of numerical methods to understand the haemodynamics. The present study aims to investigate the effects of renal artery angulation on the flow characteristics in a non-critically stenosed artery compared to that of a normal artery in order to understand better, the reasons for causes and progression of renal artery stenosis. Abdominal aorta-renal artery models ranging from 30° to 90° angulations were generated from computerized tomography-angiogram slices, post which they were subjected to cleanup and defeaturing. Haemodynamic parameters such as velocity, pressure and time-averaged wall shear stress were evaluated at early systole, peak systole and peak diastole for the different artery models. Extensive amounts of flow recirculation were observed in normal renal arteries with higher bifurcating angles, whereas it was not the case in stenosed arteries where flow acceleration was seen for the duration of the cardiac cycle. Evaluation of static pressure encountered a similar trend where an increase in angulation saw a decrease in pressure for normal arteries which contradicted with stenosed artery results. Analysis of shear stress saw very similar trends in normal and stenosed arteries, with lower angulation profiles experiencing higher values of shear stress at the Ostia. In the cases of arteries of higher angulation with a non-critical stenosis, the possibility of worsening of stenosis into an opprobrious stage remains a concern.

First-Phase Ejection Fraction, a Measure of Preclinical Heart Failure, Is Strongly Associated With Increased Mortality in Patients With COVID-19

Presence of heart failure is associated with a poor prognosis in patients with coronavirus disease 2019 (COVID-19). The aim of the present study was to examine whether first-phase ejection fraction (EF1), the ejection fraction measured in early systole up to the time of peak aortic velocity, a sensitive measure of preclinical heart failure, is associated with survival in patients hospitalized with COVID-19. A retrospective outcome study was performed in patients hospitalized with COVID-19 who underwent echocardiography (n=380) at the West Branch of the Union Hospital, Wuhan, China and in patients admitted to King’s Health Partners in South London, United Kingdom. Association of EF1 with survival was performed using Cox proportional hazards regression. EF1 was compared in patients with COVID-19 and in historical controls with similar comorbidities (n=266) who had undergone echocardiography before the COVID-19 pandemic. In patients with COVID-19, EF1 was a strong predictor of survival in each patient group (Wuhan and London). In the combined group, EF1 was a stronger predictor of survival than other clinical, laboratory, and echocardiographic characteristics including age, comorbidities, and biochemical markers. A cutoff value of 25% for EF1 gave a hazard ratio of 5.23 ([95% CI, 2.85–9.60]; P <0.001) unadjusted and 4.83 ([95% CI, 2.35–9.95], P <0.001) when adjusted for demographics, comorbidities, hs-cTnI (high-sensitive cardiac troponin), and CRP (C-reactive protein). EF1 was similar in patients with and without COVID-19 (23.2±7.3 versus 22.0±7.6%, P =0.092, adjusted for prevalence of risk factors and comorbidities). Impaired EF1 is strongly associated with mortality in COVID-19 and probably reflects preexisting, preclinical heart failure.

First phase ejection fraction in aortic stenosis; a useful new measure of early left ventricular systolic dysfunction

In aortic stenosis (AS), a left ventricular (LV) ejection fraction (EF) <50% or symptoms are class I indications for aortic valve intervention. However, an EF <50% may be too conservative since subendocardial fibrosis may already have developed. An earlier marker of LV systolic dysfunction is therefore needed and first phase EF (EF1) is a promising new candidate. It is the EF measured over early systole to the point of maximum transaortic blood flow. It may be low in the presence of preserved total LV EF since the heart may compensate by recruiting myosin motors in later systole. The EF1 is inversely related to the grade of AS and directly related to markers of subendocardial fibrosis like late gadolinium enhancement on cardiac magnetic resonance scanning. A reduced EF1 (<25%) predicts adverse clinical events better that total EF and global longitudinal strain. We suggest that it is worth exploring as an indication for surgery in patients with asymptomatic severe AS.

Abstract 16994: Left Ventricle Accessory Antero-Septal Papillary Muscle Detected in the LVOT Vicinity by Means of Cardiac MRI and Echocardiography in HOCM and Control Patients

Background: We studied by means of echocardiography (echo) and cardiac MRI the occurrence of an accessory papillary muscle that unites mostly the left ventricle (LV) apex with the basal or mid antero-septum. Methods: We included all good quality studies as reviewed by two cardiologists and assessed the occurrence of a contractile papillary muscle situated between the LV apex and antero-septum. Results: A contractile accessory papillary muscle situated between the LV apex and the antero-septum was seen in 100% of HOCM patients and 62% of control patients (p=0.05, panels 1-6 HOCM patients and 7-9 controls; panels 1, 4 and 7 - diastole; 2,5 and 8 - early-systole; 3, 6 and 9 - end-systole) in the cardiac MRI images acquired from a total of 22 HOCM (9) and control (13) patients. The same structure was observed in 241 patients representing 69.5% of all-comers echo studies. The age was 69 ± 17 years on average in the echo arm, patients harboring the antero-septal accessory muscle being older (71.6 + 15.7 years old vs 63.5 ± 18.1 for those without, p=0.0005). We exemplify this structure by parasternal long axis still echo images from 24 patients (panel 14) as well as more detailed images from 4 patients in the same group (panels 10-13). Red arrows point out the accessory antero-septal papillary muscle and white arrows the antero-septum. Pink and yellow dots neighbor the regular antero-lateral and postero-medial pap muscles and the white dots the mitral valve. Conclusion: A contractile accessory papillary muscle was observed in slightly more than half of the all-comer echo studies, and in all HOCM patients in the cardiac MRI arm. Further research is needed to fully characterize the anatomical and physiological significance of this structure attaching in the immediate vicinity of the LVOT in HOCM and control patients.

Probing cardiomyocyte mobility with multi-phase cardiac diffusion tensor MRI

Purpose Cardiomyocyte organization and performance underlie cardiac function, but the in vivo mobility of these cells during contraction and filling remains difficult to probe. Herein, a novel trigger delay (TD) scout sequence was used to acquire high in-plane resolution (1.6 mm) Spin-Echo (SE) cardiac diffusion tensor imaging (cDTI) at three distinct cardiac phases. The objective was to characterize cardiomyocyte organization and mobility throughout the cardiac cycle in healthy volunteers. Materials and methods Nine healthy volunteers were imaged with cDTI at three distinct cardiac phases (early systole, late systole, and diastasis). The sequence used a free-breathing Spin-Echo (SE) cDTI protocol (b-values = 350s/mm2, twelve diffusion encoding directions, eight repetitions) to acquire high-resolution images (1.6x1.6x8mm3) at 3T in ~7 minutes/cardiac phase. Helix Angle (HA), Helix Angle Range (HAR), E2 angle (E2A), Transverse Angle (TA), Mean Diffusivity (MD), diffusion tensor eigenvalues (λ1-2-3), and Fractional Anisotropy (FA) in the left ventricle (LV) were characterized. Results Images from the patient-specific TD scout sequence demonstrated that SE cDTI acquisition was possible at early systole, late systole, and diastasis in 78%, 100% and 67% of the cases, respectively. At the mid-ventricular level, mobility (reported as median [IQR]) was observed in HAR between early systole and late systole (76.9 [72.6, 80.5]° vs 96.6 [85.9, 100.3]°, p<0.001). E2A also changed significantly between early systole, late systole, and diastasis (27.7 [20.8, 35.1]° vs 45.2 [42.1, 49]° vs 20.7 [16.6, 26.4]°, p<0.001). Conclusion We demonstrate that it is possible to probe cardiomyocyte mobility using multi-phase and high resolution cDTI. In healthy volunteers, aggregate cardiomyocytes re-orient themselves more longitudinally during contraction, while cardiomyocyte sheetlets tilt radially during wall thickening. These observations provide new insights into the three-dimensional mobility of myocardial microstructure during systolic contraction.

Intra-aortic Balloon Pump

This chapter describes the intra-aortic balloon pump (IABP), which is the single most widely used mechanical circulatory assist device available today. Counterpulsation refers to balloon inflation in diastole and deflation in early systole: this results in increased coronary blood flow, left ventricular afterload reduction, and increased end-organ perfusion. Other uses of balloon counterpulsation include refractory ventricular arrhythmias, inability to wean from cardiopulmonary bypass, bridge to intervention in severe/critical aortic stenosis, and refractory pulmonary edema from decompensated heart failure. However, the absolute contraindications for IABP placement are aortic dissection, clinically significant aortic aneurysm, severe peripheral artery disease, significant aortic regurgitation, uncontrolled bleeding, and/or sepsis. The chapter then explains the optimal positioning for IABP. It also looks at complications associated with IABPs. These include thrombocytopenia and vascular complications, such as limb ischemia, bleeding, dissection, and hematoma/pseudoaneurysm formation. The presence of blood in the balloon tubing suggests the possibility of balloon rupture and gas embolism, an extremely uncommon but catastrophic event.

Cardiac-gated intracranial elastance in a swine model of raised intracranial pressure: a novel method to assess intracranial pressure–volume dynamics

OBJECTIVEPrevious studies have demonstrated the importance of intracranial elastance; however, methodological difficulties have limited widespread clinical use. Measuring elastance may offer potential benefit in helping to identify patients at risk for untoward intracranial pressure (ICP) elevation from small rises in intracranial volume. The authors sought to develop an easily used method that accounts for the changing ICP that occurs over a cardiac cycle and to assess this method in a large-animal model over a broad range of ICPs.METHODSThe authors used their previously described cardiac-gated intracranial balloon pump and swine model of cerebral edema. In the present experiment they measured elastance at 4 points along the cardiac cycle—early systole, peak systole, mid-diastole, and end diastole—by using rapid balloon inflation to 1 ml over an ICP range of 10–30 mm Hg.RESULTSThe authors studied 7 swine with increasing cerebral edema. Intracranial elastance rose progressively with increasing ICP. Peak-systolic and end-diastolic elastance demonstrated the most consistent rise in elastance as ICP increased. Cardiac-gated elastance measurements had markedly lower variance within swine compared with non–cardiac-gated measures. The slope of the ICP–elastance curve differed between swine. At ICP between 20 and 25 mm Hg, elastance varied between 8.7 and 15.8 mm Hg/ml, indicating that ICP alone cannot accurately predict intracranial elastance.CONCLUSIONSMeasuring intracranial elastance in a cardiac-gated manner is feasible and may offer an improved precision of measure. The authors’ preliminary data suggest that because elastance values may vary at similar ICP levels, ICP alone may not necessarily best reflect the state of intracranial volume reserve capacity. Paired ICP–elastance measurements may offer benefit as an adjunct “early warning monitor” alerting to the risk of untoward ICP elevation in brain-injured patients that is induced by small increases in intracranial volume.

Duration of early systolic lengthening: prognostic potential in the general population

Background When the left ventricle pressure rises during early systole, myocardial fibres with reduced contractility tend to stretch instead of shortening. This interval is known as duration of early systolic lengthening (DESL). We sought to investigate if DESL provides prognostic information on cardiovascular events. Methods and results In this prospective study we included 1210 participants from a low-risk general population who underwent speckle tracking echocardiography (men 41%, mean age 56 years, SD 16). Primary endpoints were incident heart failure (HF), myocardial infarction (MI), and cardiovascular death (CVD). We defined DESL as time from onset of Q-wave on the electrocardiogram to peak positive systolic strain. In addition, we assessed the ratio between DESL and duration of cardiac systole, DESLsystole. During median follow-up of 16 years, 90 (7%) developed HF, 50 (4%) MI, and 70 (6%) experienced CVD. Both DESL [hazard ratio (HR) 1.58 95%CI 1.16–2.15, P = 0.004 per 10 ms increase] and DESLsystole (HR 1.74 95%CI 1.24–2.47, P = 0.001 per 1% increase) were predictors of HF. Similarly, DESL (HR 1.40 95%CI 1.09–1.78, P = 0.007 per 10 ms increase) and DESLsystole (HR 1.58 95%CI 1.01–2.49, P = 0.047 per 1% increase) were predictors of MI. No associations were found with CVD. After adjusting for clinical and echocardiographic parameters, the associations remained significant. DESLsystole was superior to systolic echocardiographic parameters for predicting HF (P = 0.012). Conclusion DESL and the novel index of DESLsystole provide independent and novel prognostic information on the risk of HF and MI in the general population. Evaluation of DESL should be explored in future echocardiographic studies.

The mechanism of mitral regurgitant jets identified by 3-dimensional transesophageal echocardiography

This study is a case report, which presents a case of severe mitral regurgitation in a 77-year-old man. Two-dimensional transesophageal echocardiography (TEE), regurgitant jets directed anteriorly in early systole and centrally to laterally in late systole were seen, while three-dimensional TEE showed a flail posterior middle scallop not only angulated centrally, but also laterally, which provided insight into the mechanism of mitral regurgitant jet direction. This case demonstrates the clinical usefulness of 3-dimensional TEE for identifying the mechanism of mitral regurgitant jets.The institution where the figures and the videos were recorded: Division of Cardiology, Mazankowski Alberta Heart Institute, University of Alberta Hospital, Edmonton, Alberta, Canada.

Septal flash and septal rebound stretch have different underlying mechanisms

Abnormal left-right motion of the interventricular septum in early systole, known as septal flash (SF), is frequently observed in patients with left bundle branch block (LBBB). Transseptal pressure gradient and early active septal contraction have been proposed as explanations for SF. Similarities in timing (early systole) and location (septum) suggest that SF may be related to septal systolic rebound stretch (SRSsept). We aimed to clarify the mechanisms generating SF and SRSsept. The CircAdapt computer model was used to isolate the effects of timing of activation of the left ventricular free wall (LVFW), right ventricular free wall (RVFW), and septum on SF and SRSsept. LVFW and septal activation times were varied by ±80 ms relative to RVFW activation time. M-mode-derived wall motions and septal strains were computed and used to quantify SF and SRSsept, respectively. SF depended on early activation of the RVFW relative to the LVFW. SF and SRSsept occurred in LBBB-like simulations and against a rising transseptal pressure gradient. When the septum was activated before both LVFW and RVFW, no SF occurred despite the presence of SRSsept. Computer simulations therefore indicate that SF and SRSsept have different underlying mechanisms, even though both can occur in LBBB. The mechanism of leftward motion during SF is early RVFW contraction pulling on and straightening the septum when unopposed by the LVFW. SRSsept is caused by late LVFW contraction following early contraction of the septum. Changes in transseptal pressure gradient are not the main cause of SF in LBBB.