Predictors of mitral valve hemodynamics after mitral valve repair for degenerative mitral regurgitation: a subanalysis of the CAMRA randomized trial

Introduction

Intra-operative predictors of mid-to-late mitral valve dysfunction after surgical repair of mitral regurgitation (MR) caused by prolapse remain poorly characterized. This study aims to evaluate the effect of annuloplasty prosthesis size on post-operative MV hemodynamics at rest and during exercise, and to identify perioperative predictors of MV dysfunction.

Methods

104 patients were randomly assigned to resection and preservation for surgical treatment of posterior leaflet prolapse in the Canadian Mitral Research Alliance CardioLink-2 study. Echocardiograms were performed at baseline and 1 year postoperatively. Intraoperative TEE was performed to assess immediate MV gradients. Exercise TTE was performed 1 year after repair. Linear regression analysis was used to identify associations between MV indices (rest and peak exercise gradients) at 12 months, and perioperative echocardiographic and clinical factors.

Results

Mean age of participants was 65±10 years, and 83% were male. Larger annuloplasty size was associated with lower transmitral gradients at rest and during peak exercise. In multivariable analysis, annuloplasty size ≥34mm was associated with lower mean and peak rest and exercise gradients at 12 months, after adjustment for repair type, age, sex, and BSA (p<0.001). Higher pre-operative pulmonary artery pressures were associated with reduced functional capacity post-operatively. Intra-operative TEE gradients predict resting and exercise MV hemodynamics at 1 year.

Conclusion

Annuloplasty size ≥34mm is associated with improved MV hemodynamics at rest and during peak exercise 1 year post MV repair. MV repair prior to onset of pulmonary hypertension confers favourable post operative functional capacity. Finally, intra-operative TEE can be used to identify patients at risk of mitral valve dysfunction within 1 year of repair.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): The Heart and StrokeFoundation of Ontario (GIA 16-00014666)

A randomized surgical trial of mitral valve repair with leaflet resection versus leaflet preservation on functional mitral stenosis – primary results of the CAMRA CardioLink-2 trial

Background

The gold standard treatment for mitral valve regurgitation due to prolapse involves surgery with annuloplasty and either leaflet resection or leaflet preservation, with placement of artificial neochordae. It has been suggested that leaflet resection may be prone to functional mitral stenosis, whereby a patient may have a higher mitral gradient at peak exercise compared to a leaflet preservation strategy. Although both techniques are widely used, there has been no prospective randomized study conducted to compare these two techniques, particularly in regard to functional mitral stenosis.

Methods

A total of 104 patients with posterior leaflet prolapse were randomized to undergo mitral repair with either leaflet resection (N=54) or leaflet preservation (N=50) at 7 specialized Canadian cardiac centers. Patient age, proportion of female patients, and mean Society of Thoracic Surgeons risk score was 63.9±10.4 years, 19%, and 1.4% for those who underwent leaflet resection, and 66.3±10.8 years, 16%, and 1.9% for those who underwent leaflet preservation, respectively. The primary endpoint was the mean trans-mitral repair gradient at peak exercise 12-months after repair.

Results

Baseline characteristics were similar between the groups. At 12-months, the mean trans-mitral repair gradient at peak exercise in patients who underwent leaflet resection and preservation was 9.1±5.2 and 8.3±3.3 mmHg (P=0.4), respectively. The two groups had similar mean mitral valve gradient at rest (3.2±1.9 mmHg following resection and 3.1±1.1 mmHg following leaflet preservation, P=0.7). There was no between-group difference for the 6-minute walk distance (451±147 m and 481±95 m for the resection and preservation groups, respectively, P=0.3).

Conclusion

We report the first prospective surgical randomized trial to evaluate commonly used mitral valve repair strategies for posterior leaflet prolapse. Leaflet resection and leaflet preservation both yield acceptable results with no difference in postoperative valve gradient and functional status 12-months after surgical mitral valve repair.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Heart and Stroke Foundation of Canada

P1500Effects of empagliflozin on cardiac function in patients with type 2 diabetes mellitus: echocardiographic substudy of the EMPA-HEART cardiolink-6 trial

Background

The EMPA-HEART trial showed a reduction in left ventricular (LV) mass index by cardiac MRI at 6 months in patients treated with Empagliflozin vs placebo. A secondary analysis of key echocardiographic parameters was performed to provide further insight into the mechanism of LV remodeling.

Methods

All patients enrolled prospectively underwent transthoracic echocardiography (TTE) at baseline and at 6 months. Measurements were performed according to the American Society of Echocardiography guidelines. Key outcomes of interest included changes in diastolic function and right ventricle parameters at 6 months in patients treated with Empagliflozin vs placebo.

Results

A total of 97 patients were enrolled (49 treated with Empagliflozin and 48 in the placebo group). There was no significant difference in the change in average E/E' at 6-months in the Empagliflozin group vs placebo (−0.4 vs +0.2, adjusted difference −0.2, 95% CI [−1.3 to 0.82], p=0.7) Similarly, there was no difference between the groups in secondary TTE parameters (Table 1). Subgroup analyses showed no benefit among patients with baseline LVEF >50% vs. ≤50%, and baseline LV mass index ≥60 g/m2 vs <60 g/m2.

Echocardiographic Parameter Placebo (n=48) Empagliflozin (n=49) Adjusted Difference Between Groups 95% CI P-Value Baseline 6 months Change Baseline 6 months Change LVEF (%)* 55.5 (8.7) 54.3 (8.9) −1.0 (6.5) 58.0 (7.5) 59.1 (8.57) 0.72 (5.1) 2.2 (−0.2, 4.7) 0.1 Diastolic Parameters:   Average E/e' 10.1 (3.1) 10.3 (2.5) 0.2 (3.0) 10.6 (3.0) 10.5 (3.6) −0.4 (2.5) −0.2 (−1.3, 0.8) 0.7   Medial E/e' 12.3 (3.9) 12.5 (3.6) 0.1 (3.7) 12.6 (4.2) 12.6 (5.2) −0.3 (3.3) −0.3 (−1.7, 1.1) 0.7   Lateral E/e' 8.0 (2.8) 8.2 (2.2) 0.2 (2.7) 8.7 (2.6) 8.4 (2.5) −0.4 (2.7) −0.1 (−1.0, 0.8) 0.8   E velocity (cm/sec) 68.6 (15.2) 70.6 (14.7) 1.8 (15.4) 74.4 (18.2) 71.2 (16.8) −3.2 (15.1) −2.3 (−7.9, 3.3) 0.4   A velocity (cm/sec) 74.7 (17.9) 77.9 (18.8) 2.9 (15.9) 76.2 (16.5) 75.8 (14.5) −1.4 (11.7) −3.5 (−8.9, 1.6) 0.2   LA volume index (mL/m2) 32.7 (7.9) 30.8 (8.1) −2.0 (6.7) 30.2 (6.7) 28.7 (5.5) −1.6 (6.5) −0.9 (−3.4, 1.6) 0.5 RV Parameters:   TAPSE (cm) 1.8 (0.5) 1.8 (0.4) 0.1 (0.4) 2.0 (1.2) 1.8 (0.4) −0.3 (1.4) −0.1 (−0.3, 0.1) 0.3   RV S' TDI (cm/sec) 10.9 (2.9) 10.6 (2.5) −0.1 (2.2) 10.4 (2.7) 10.2 (2.6) −0.4 (2.0) −0.3 (−1.2, 0.5) 0.4 *Measured by cardiac MRI. LA, left atrium; LVEF, left ventricular ejection fraction; RV, right ventricle; TAPSE, tricuspid annular plane systolic excursion; TDI, tissue Doppler imaging. Data expressed as mean (standard deviation).

Conclusion

This study showed no significant change in key echocardiographic parameters in patients treated with Empagliflozin, suggesting that changes in loading conditions induced by empagliflozin (i.e. preload) do not mediate the reduction in LV mass.

P2618Association of left ventricular ejection fraction with mortality and hospitalizations

Background

Although 2-dimensional echocardiography (2DE) is widely used to measure left ventricular ejection fraction (LVEF), the prognostic value of 2DE-derived LVEF has not been clearly demonstrated in a broad range of patients, including those acutely hospitalized as well as ambulatory patients. In particular, the prognostic value of echocardiographic LVEF has not been demonstrated for cardiovascular and heart failure hospitalizations.

Purpose

To determine if greater degrees of LV dysfunction are associated with progressively increasing risks of death or cardiovascular hospitalizations among patients undergoing echocardiography in hospital or outpatient settings.

Methods

We examined quantitative LVEFs from patient-level echocardiographic reports at 3 large hospital laboratories, which were linked to the Canadian Institute for Health Information hospitalization database and to death registries in Ontario, Canada. LVEF was categorized as <25%, 25–35%, 36–45%, or 46–55% (reference). Analyses were performed using cause-specific hazard competing risk models and stratified by: a) outpatient vs. inpatient echocardiogram, and b) if inpatient study, whether the reason for hospitalization was cardiac or noncardiac in nature.

Results

In the echocardiographic cohort of 27,323 patients (median age 68 [IQR: 58–77], 14,828 women [31.7%]), greater reductions in LVEF were associated with higher rates of all-cause mortality, with adjusted hazard ratios (95% CI) of 1.67 (1.57, 1.77) for LVEF <25%, 1.30 (1.24, 1.36) for LVEF 25–35%, and 1.17 (1.11, 1.23) for LVEF 36–45%, compared to LVEF 46–55% (all p<0.001). The cumulative incidence of cardiovascular death was higher as LVEF progressively worsened (Figure). The rate of heart failure hospitalizations was also increased with hazard ratios of 1.71 (1.59, 1.85) for LVEF <25%, 1.39 (1.31, 1.48) for LVEF 25–35%, and 1.21 (1.13, 1.29) for LVEF 36–45%, compared to LVEF 46–55% (all p<0.001). Cardiovascular hospitalizations were also increased with hazard ratios of 1.35 (1.27, 1.42), 1.21 (1.16, 1.27), and 1.13 (1.07, 1.18) for LVEFs <25%, 25–35%, and 36–45%, respectively (all p<0.001). The risk of mortality and hospitalizations increased comparably with greater reductions in LVEF during both inpatient cardiac or noncardiac admissions (p<0.001).

Cumulative incidence of CV death

Conclusions

Quantitative LVEF assessed by 2DE is potent prognostically and was able to stratify the risk of both death and hospitalization outcomes in a wide range of clinical settings. Patients with reduced LVEF measured on inpatient or outpatient echocardiograms, and even in the context of non-cardiac admission, should be considered an at-risk group in whom quality of care metrics could be evaluated in future studies.

Acknowledgement/Funding

Canadian Institutes of Health Research, Heart and Stroke Foundation, and the Ted Rogers Centre for Heart Research

Quantitative assessment of brain microvascular and tissue oxygenation during cardiac arrest and resuscitation in pigs

Cardiac arrest is associated with a very high rate of mortality, in part due to inadequate tissue perfusion during attempts at resuscitation. Parameters such as mean arterial pressure and end-tidal carbon dioxide may not accurately reflect adequacy of tissue perfusion during cardiac resuscitation. We hypothesised that quantitative measurements of tissue oxygen tension would more accurately reflect adequacy of tissue perfusion during experimental cardiac arrest. Using oxygen-dependent quenching of phosphorescence, we made measurements of oxygen in the microcirculation and in the interstitial space of the brain and muscle in a porcine model of ventricular fibrillation and cardiopulmonary resuscitation. Measurements were performed at baseline, during untreated ventricular fibrillation, during resuscitation and after return of spontaneous circulation. After achieving stable baseline brain tissue oxygen tension, as measured using an Oxyphor G4-based phosphorescent microsensor, ventricular fibrillation resulted in an immediate reduction in all measured parameters. During cardiopulmonary resuscitation, brain oxygen tension remained unchanged. After the return of spontaneous circulation, all measured parameters including brain oxygen tension recovered to baseline levels. Muscle tissue oxygen tension followed a similar trend as the brain, but with slower response times. We conclude that measurements of brain tissue oxygen tension, which more accurately reflect adequacy of tissue perfusion during cardiac arrest and resuscitation, may contribute to the development of new strategies to optimise perfusion during cardiac resuscitation and improve patient outcomes after cardiac arrest.

S100B interaction with the receptor for advanced glycation end products (RAGE): a novel receptor-mediated mechanism for myocyte apoptosis postinfarction

RATIONALE

Post-myocardial infarction ventricular remodeling is associated with the expression of a variety of factors including S100B that can potentially modulate myocyte apoptosis.

OBJECTIVE

This study was undertaken to investigate the expression and function of S100B and its receptor, the receptor for advanced glycation end products (RAGE) in both postinfarction myocardium and in a rat neonatal myocyte culture model.

METHODS AND RESULTS

In a rat model of myocardial infarction following coronary artery ligation, we demonstrate in periinfarct myocytes, upregulation of RAGE, induction of S100B, and release into plasma with consequent myocyte apoptosis. Using a coimmunoprecipitation strategy, we demonstrate a direct interaction between S100B and RAGE. In rat neonatal cardiac myocyte cultures, S100B at concentrations > or = 50 nmol/L induced myocyte apoptosis, as evidenced by increased terminal DNA fragmentation, TUNEL, cytochrome c release from mitochondria to cytoplasm, phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and p53, increased expression and activity of proapoptotic caspase-3, and decreased expression of antiapoptotic Bcl-2. Transfection of a full-length cDNA of RAGE or a dominant-negative mutant of RAGE resulted in increased or attenuated S100B-induced myocyte apoptosis, respectively. Inhibition of ERK1/2 by U0126/PD-98059 or overexpression of a dominant negative p53 comparably inhibited S100B-induced myocyte apoptosis.

CONCLUSIONS

These results suggest that interaction of RAGE and its ligand S100B after myocardial infarction may play a role in myocyte apoptosis by activating ERK1/2 and p53 signaling. This receptor-mediated mechanism is uniquely amenable to therapeutic intervention.

CCS/CAR/CANM/CNCS/CanSCMR joint position statement on advanced noninvasive cardiac imaging using positron emission tomography, magnetic resonance imaging and multidetector computed tomographic angiography in the diagnosis and evaluation of ischemic heart disease--executive summary

BACKGROUND

Over the past few decades, advanced imaging modalities with excellent diagnostic capabilities have emerged. The aim of the present position statement was to systematically review existing literature to define Canadian recommendations for their clinical use.

METHODS

A systematic literature review to 2005 was conducted for positron emission tomography (PET), multidetector computed tomographic angiography and magnetic resonance imaging (MRI) in ischemic heart disease. Papers that met the criteria were reviewed for accuracy, prognosis data and study quality. Recommendations were presented to primary and secondary panels of experts, and consensus was achieved.

RESULTS

Indications for PET include detection of coronary artery disease (CAD) with perfusion imaging, and defining viability using fluorodeoxyglucose to determine left ventricular function recovery and/or prognosis after revascularization (class I). Detection of CAD in patients, vessel segments and grafts using computed tomographic angiography was considered class IIa at the time of the literature review. Dobutamine MRI is class I for CAD detection and, along with late gadolinium enhancement MRI, class I for viability detection to predict left ventricular function recovery. Imaging must be performed at institutions and interpreted by physicians with adequate experience and training.

CONCLUSIONS

Cardiac imaging using advanced modalities (PET, multidetector computed tomographic angiography and MRI) is useful for CAD detection, viability definition and, in some cases, prognosis. These modalities complement the more widespread single photon emission computed tomography and echocardiography. Given the rapid evolution of technology, initial guidelines for clinical use will require regular updates. Evaluation of their integration in clinical practice should be ongoing; optimal use will require proper training. A joint effort among specialties is recommended to achieve these goals.

Quantification of myocardial perfusion and determination of coronary stenosis severity during hyperemia using real-time myocardial contrast echocardiography

Although regional myocardial perfusion can be currently quantified with myocardial contrast echocardiography (MCE) by using intermittent harmonic imaging (IHI), the method is tedious and time-consuming in the clinical setting. We hypothesized that regional myocardial perfusion can be quantified and the severity of coronary stenosis determined during hyperemia with MCE using real-time imaging (RTI) where microbubbles are not destroyed. Six open-chest dogs were studied during maximal hyperemia induced by adenosine in the absence or presence of coronary stenoses varying from mild to severe. Myocardial blood flow (MBF) was measured at each stage by using radiolabeled microspheres. MCE was performed using both IHI and RTI. Data for the latter were acquired in both end-systole and end-diastole. No differences were found between myocardial flow velocity (MFV) derived from IHI and RTI when end-systolic frames were used for the latter. MFV was consistently higher for RTI (P <.01) when end-diastolic frames were used. A linear relation was noted between MFV and radiolabeled microsphere-derived MBF ratios from the stenosed and the normal beds when end-systolic frames were used for RTI (r = 0.78, P <.001), whereas no relation was found when end-diastolic frames were used (r = 0.08, P =.78). The scatter for assessing MBF (A.beta) was minimal for IHI and RTI (9%-10%) with end-systolic frames, whereas that for RTI with end-diastolic frames was large (30%). Furthermore the correlation with radiolabeled microsphere-derived MBF was significantly (P <.01) weaker with RTI when end-diastolic frames were used (r = 0.53) than when end-systolic frames (r = 0.94) or IHI was used (r = 0.99). Data acquisition for IHI was 10 minutes, whereas it was 8 seconds for RTI. Thus, RTI can be used to quantify regional myocardial perfusion and stenosis severity during MCE. Only end-systolic frames, however, provide accurate data. RTI offers a rapid and easy means of assessing regional myocardial perfusion with MCE.

Decrease in coronary blood flow reserve during hyperlipidemia is secondary to an increase in blood viscosity

BACKGROUND

During maximal hyperemia, capillaries provide the greatest resistance to flow. A major determinant of capillary resistance is viscosity. We, therefore, hypothesized that abnormal coronary blood flow (CBF) reserve observed during hyperlipidemia is secondary to increased blood viscosity and not abnormal coronary vasomotion.

METHODS AND RESULTS

Maximal hyperemia was induced in 9 dogs using adenosine. Serum triglyceride levels were increased by incremental doses of Intralipid. A good correlation was noted between serum triglyceride levels and blood viscosity (r=0.82). Neither total coronary blood volume nor myocardial blood volume changed with increasing serum triglyceride levels, indicating lack of vasomotion. Myocardial vascular resistance (MVR) increased with increasing triglyceride levels (r=0.84), while hyperemic myocardial blood flow (MBF) decreased (r=-0.64). The decrease in hyperemic MBF was associated with a decrease in blood velocity (r=-0.56). These findings were confirmed with direct intravital microscopic observations in the mice cremaster muscle.

CONCLUSIONS

Increasing lipid levels in a fully dilated normal coronary bed causes no change in large or small vessel dimensions. Instead, the increase in blood viscosity causes capillary resistance to rise, which attenuates hyperemic CBF. Therefore, the abnormal CBF reserve associated with hyperlipidemia is due to increase blood viscosity and not abnormal vascular function.

Quantification of cerebral perfusion with "Real-Time" contrast-enhanced ultrasound

BACKGROUND

No noninvasive technique is currently capable of "real-time" assessment and monitoring of cerebral blood flow (CBF). We hypothesized that cerebral perfusion could be accurately measured and monitored in "real time" with contrast-enhanced ultrasound (CEU).

METHODS AND RESULTS

Cerebral perfusion was assessed in 9 dogs through a craniotomy with CEU at baseline and during hypercapnia and hypocapnia while normoxia was maintained. Cerebral microvascular blood volume (A), microbubble velocity (beta), and blood flow (Axbeta) were calculated from time-versus-acoustic intensity relations. Compared with baseline, hypercapnia and hypocapnia significantly increased and decreased CBF, respectively, as measured by CEU. These changes in blood flow were mediated by changes in both A and beta. A good correlation was found between Axbeta derived from CEU and CBF measured by radiolabeled microspheres (y=0.67x-0.04, r=0.91, P<0.001).

CONCLUSIONS

Changes in both cerebral microvascular blood volume and red blood cell velocity can be accurately assessed with CEU. Thus, CEU has the potential for bedside measurement and monitoring of cerebral perfusion in real time in patients with craniotomies or burr holes.