Right ventricular function and long-term clinical outcomes after cardiac resynchronization therapy: A cardiovascular magnetic resonance study

BACKGROUND

Right ventricular (RV) dysfunction has been linked to a poor response to cardiac resynchronization therapy (CRT). We sought to determine whether cardiovascular magnetic resonance (CMR)-derived measures of RV function influence clinical outcomes after CRT.

METHODS

In this retrospective study, we used cardiovascular magnetic resonance (CMR) to assess pre-implant RV volumes and RV ejection fraction (RVEF) in relation to clinical outcomes after CRT implantation.

RESULTS

Among 243 patients (age: 70.3 ± 10.8 years [mean ±. SD]; 68.7% male; 121 [49.8%]) with ischemic cardiomyopathy and 122 (50.2%) with non-ischemic cardiomyopathy, 141 (58%) after CRT-defibrillation and 102 (42%) after CRT-pacing, 101 (41.6.0%) patients died, 61 (25.1%) from cardiac causes and 24 (9.88%) from non-cardiac causes, over 5.87 years (median; interquartile range: 4.35-7.73). Two (0.82%) patients underwent cardiac transplantation and 4 (1.64%) had a left ventricular assist device. A total of 41 (16.9%) met the composite endpoint of sudden cardiac death, ventricular tachycardia or ventricular fibrillation. In univariate analyses, no measure of RV function was associated with total mortality or the arrhythmic endpoint. RVEF was associated with cardiac mortality on univariate analyses (HR per 10%: 0.82, 95% CI 0.70-0.96), but not on multivariate analyses that included left ventricular ejection fraction.

CONCLUSIONS

There is no relationship between measures of RV function, such as RV volumes and RVEF, and the long-term clinical outcome of CRT. These findings indicate that such measures should not be considered in patient selection. This article is protected by copyright. All rights reserved.

Assessing heart disease using a novel magnetocardiography device

The aim of this paper is to present the use of a portable, unshielded magnetocardiograph (MCG) and identify key characteristics of MCG scans that could be used in future studies to identify parameters that are sensitive to cardiac pathology. We recruited 50 patients with confirmed myocardial infarction (MI) within the past 12 weeks and 46 volunteers with no history of cardiac disease. A set of 38 parameters were extracted from MCG features including both signals from the sensor array and from magnetic images obtained from the device and principal component analysis was used to concentrate the information contained in these parameters into uncorrelated predictors. Linear fits of these parameters were then used to examine the ability of MCG to distinguish between sub-groups of patients. In the fist instance, the primary aim of this study was to ensure that MCG has a basic ability to separate a highly polarised patient group (young controls from post infarction patients) and to identify parameters that could be used in future studies to build a formal diagnostic tool kit. Parameters that parameterised left ventricular ejection fraction (LVEF) were identified and an example is presented to show differential low and high ejection fractions.

Randomized double-blind placebo-controlled trial of perhexiline in heart failure with preserved ejection fraction syndrome

Recently heart failure with preserved ejection fraction (HFpEF) has emerged as a huge epidemic. Increasing evidence shows the role of energy deficiency in the pathophysiology of HFpEF. In the current study, we hypothesize that the use of metabolic modulator perhexiline would correct myocardial energy deficiency and improve exercise capacity and diastolic abnormalities in patients with this syndrome.

Short-term intravenous sodium nitrite infusion improves cardiac and pulmonary hemodynamics in heart failure patients

BACKGROUND

Nitrite exhibits hypoxia-dependent vasodilator properties, selectively dilating capacitance vessels in healthy subjects. Unlike organic nitrates, it seems not to be subject to the development of tolerance. Currently, therapeutic options for decompensated heart failure (HF) are limited. We hypothesized that by preferentially dilating systemic capacitance and pulmonary resistance vessels although only marginally dilating resistance vessels, sodium nitrite (NaNO2) infusion would increase cardiac output but reduce systemic arterial blood pressure only modestly. We therefore undertook a first-in-human HF proof of concept/safety study, evaluating the hemodynamic effects of short-term NaNO2 infusion.

METHODS AND RESULTS

Twenty-five patients with severe chronic HF were recruited. Eight received short-term (5 minutes) intravenous NaNO2 at 10 μg/kg/min and 17 received 50 μg/kg/min with measurement of cardiac hemodynamics. During infusion of 50 μg/kg/min, left ventricular stroke volume increased (from 43.22±21.5 to 51.84±23.6 mL; P=0.003), with marked falls in pulmonary vascular resistance (by 29%; P=0.03) and right atrial pressure (by 40%; P=0.007), but with only modest falls in mean arterial blood pressure (by 4 mm Hg; P=0.004). The increase in stroke volume correlated with the increase in estimated trans-septal gradient (=pulmonary capillary wedge pressure-right atrial pressure; r=0.67; P=0.003), suggesting relief of diastolic ventricular interaction as a contributory mechanism. Directionally similar effects were observed for the above hemodynamic parameters with 10 μg/kg/min; this was significant only for stroke volume, not for other parameters.

CONCLUSIONS

This first-in-human HF efficacy/safety study demonstrates an attractive profile during short-term systemic NaNO2 infusion that may be beneficial in decompensated HF and warrants further evaluation with longer infusion regimens.

Kussmaul Physiology in Patients With Heart Failure

Background—

A paradoxical inspiratory rise in right atrial pressure (in contrast to the normal fall during inspiration), Kussmaul sign, has been described in congestive heart failure (CHF). However, the clinical and hemodynamic characteristics and clinical outcomes of patients with CHF and Kussmaul physiology have not been studied.

Methods and Results—

This is a single-center study of consecutive ambulant patients with CHF (New York Heart Association class III/IV) referred for assessment for heart transplantation between November 2011 and April 2013. Kussmaul physiology was defined as inspiratory rise in right atrial pressure during right heart catheterization. Clinical, biochemical, echocardiographic, and hemodynamic correlates were studied and outcomes assessed in patients with or without Kussmaul physiology after a mean follow-up of 379±227 days. Ninety ambulant patients (age, 53±12 years; 86% men) with CHF were studied. Kussmaul physiology was demonstrated in 39 (43%) patients, and it was associated with higher pulmonary pressures and lower cardiac index and pulmonary capacitance (all P <0.05). Patients with Kussmaul physiology were more likely to be treated with higher doses of diuretics, while higher filling pressures, N-terminal pro–B natriuretic peptide levels, and hyponatremia reflected greater neurohormonal activation. Echocardiography revealed greater left and right ventricular dimensions/volumes, restrictive transmitral filling pattern, and lower left ventricular ejection fraction and lower tricuspid annular plane systolic excursion. Peak oxygen uptake was low and comparable in both groups, but ventilation slope was higher in patients with Kussmaul physiology who also had a higher incidence of post-transplant right ventricular failure and overall mortality ( P <0.05).

Conclusions—

Kussmaul physiology is common in patients with CHF referred for heart transplantation and is associated with adverse cardiopulmonary hemodynamics. As a result of the latter, Kussmaul physiology is associated with poorer clinical outcomes. Kussmaul physiology may be useful during assessment of right heart function and pulmonary pressures before transplantation.

Effect of potential therapeutic agents in reducing oxidative stress in pulmonary tissues of recurrent airway obstruction-affected and clinically healthy horses

REASONS FOR PERFORMING STUDY

To determine and compare the reactive oxygen and nitrogen species (ROS and RNS) in pulmonary tissues of horses affected with recurrent airway obstruction (RAO) and clinically healthy horses, and to evaluate the effectiveness of potential therapeutic agents in reducing ROS and RNS in the tissues of these horses.

OBJECTIVES

We hypothesised that RAO-affected horses would have high levels of reactive species and that the test agents would reduce them. The objectives were as follows: 1) to determine the level of ROS and RNS in pulmonary tissues (bronchial and arterial rings) of RAO-affected and clinically healthy horses; and 2) to determine the ability of pentoxifylline, pyrrolidine-dithiocarbamate and a combined use of endothelin A and B receptor antagonists (BQ123 and BQ788, respectively) in reducing reactive species.

METHODS

Arterial and bronchial rings were collected from the diaphragmatic lung lobe of each horse immediately after euthanasia. The levels of ROS and RNS were measured in control tissues and those incubated with test agents, using an electron paramagnetic resonance instrument.

RESULTS

The levels of ROS and RNS were significantly greater in arterial and bronchial tissues of RAO-affected than of clinically healthy horses. Pentoxifylline and endothelin antagonists reduced both ROS and RNS in tissues from RAO-affected horses. Basal levels of reactive species in clinically healthy horses were not affected by these agents. No difference in the level of reactive species was observed between arterial and bronchial tissues.

CONCLUSIONS

Horses affected by RAO had higher ROS and RNS than clinically healthy horses. Pentoxifylline and endothelin antagonists effectively reduced ROS and RNS in pulmonary tissues of RAO-affected horses.

POTENTIAL RELEVANCE

The study suggested a potential use for pentoxifylline and endothelin antagonists in treating RAO-affected horses. As endothelin is involved in physiological functions, therapeutic use of its antagonists is cautioned.

An approach to echocardiography in hypertrophic cardiomyopathy and other causes of LVH

Hypertrophic cardiomyopathy (HCM) is the most prevalent genetic cardiovascular disease with a prevalence of 1:500 in the general population. Its identification is of critical importance as it is a common cause of sudden death in the young and can lead to considerable morbidity, including heart failure and atrial fibrillation. There are several conditions that can mimic the phenotypic appearance of HCM on echocardiography. Echocardiography remains an invaluable tool in both initial diagnosis and regular surveillance of patients with this condition. Although no single echocardiographic parameter is ideal, a structured and comprehensive assessment of cardiac structure and function will provide invaluable clues to the diagnosis and often hint towards an alternate diagnosis. The purpose of this review is to reassess the typical echocardiographic features of HCM and to highlight echocardiographic features that may help to distinguish other causes of left ventricular hypertrophy (LVH).

Device therapy in hypertrophic cardiomyopathy

With increasing awareness of the condition and particular attention being paid to family screening, the number of patients being diagnosed with hypertrophic cardiomyopathy is increasing. Although the majority of patients remain at low risk for sudden cardiac death, all patients need to undergo rigorous and ongoing risk factor stratification in order to best identify those at high risk. Although implantable cardioverter-defibrillators have proven to be effective in the prevention of sudden cardiac death, careful consideration of device implantation in high-risk patients is necessary in view of the potential for device complications and their impact on quality of life.

Magnetic resonance spectroscopy in myocardial disease

31-phosphorous ((31)P) magnetic resonance spectroscopy (MRS) is a technique that allows the noninvasive characterization of the biochemical and metabolic state of the myocardium in vivo. MRS is a pure form of molecular imaging using magnetic resonance signals from nuclei with nuclear spin to assess cardiac metabolism without the need for external radioactive tracers. (31)P MRS provides information on the underlying metabolic abnormalities that are fundamental to common conditions including ischemic heart disease, cardiomyopathy, hypertrophy and valvular disease. (31)P MRS could potentially also have a role to play in assessing response to therapy as well as the effectiveness of metabolic modulating agents. However, the use of MRS is currently limited to research due to its poor reproducibility, low spatial and temporal resolution, and long acquisition times. With technical advances in both the spectrometers and postprocessing, MRS is likely to play a role in the future of multimodal noninvasive cardiac assessment.

Death and dying in heart failure with normal ejection fraction

The overall mortality rate in patients with heart failure with normal ejection fraction (HFNEF) appears to be comparable to that in patients with heart failure with reduced ejection fraction. In contrast to the latter group of patients, randomized trials with neurohumoral blockade in patients with HFNEF have failed to demonstrate reduction in mortality. This is at least in part related to the lower proportion of heart failure-related death in the overall population of patients with HFNEF. In conclusion, better characterization of patients with HFNEF at greatest risk for heart failure-related death and understanding the risks of the different modes of death would allow more effective use of specific heart failure medical or device therapy in patients with HFNEF.

Characterization of a novel intraocular drug-delivery system using crystalline lipid antiviral prodrugs of ganciclovir and cyclic cidofovir

PURPOSE

In an earlier study, a novel intraocular drug-delivery system was reported in which hexadecyloxypropyl-phospho-ganciclovir (HDP-P-GCV) was used as a prototype. The hypothesis was that many biologically effective compounds could be modified to crystalline lipid prodrugs and could be delivered directly into the vitreous in a long-lasting, slow-release form. This study was undertaken to characterize this new drug-delivery system further, by using small particles of HDP-P-GCV and hexadecyloxypropyl-cyclic cidofovir (HDP-cCDV).

METHODS

HDP-P-GCV was microfluidized into 4.4-microm (median) particles, injected into rabbit vitreous. The vitreous drug level was then measured at different time points. Crystalline HDP-cCDV was synthesized, suspended in 5% dextrose, and injected into the rabbit's vitreous at 10, 55, 100, 550, or 1000 microg in 50 microL vehicle per eye, to determine the highest nontoxic dose. The dose, 100 microg, was injected into 24 rabbit eyes, to evaluate pharmacokinetics; into 14 rabbit eyes with established HSV retinitis, to evaluate its efficacy; and into 58 rabbit eyes before herpes simplex virus (HSV) infection to evaluate its intraocular antiviral duration.

RESULTS

Microfluidized particles of HDP-P-GCV showed an increased drug release rate compared with the large-particle drug formulation, with area under concentration-time curve (AUC) of 219.8 +/- 114.1 (n=3) versus 108.3 +/- 47.2 (n=3) for unmodified HDP-P-GCV during the 12-week period after a 2.8-micromole intravitreal injection. There was a 103% increase of the drug released from the microfluidized formulation of HDP-P-GCV versus the unmodified formulation. Intravitreal injections of HDP-cCDV at doses of 100 microg/eye or lower were not toxic. After the 100 microg/eye injections, HPLC analysis showed a vitreous HDP-cCDV level of 0.05 microM at week 5, which declined to 0.002 microM at week 8. The concentration at week 8 (0.002 microM) remained above the IC50 for cytomegalovirus (0.0003 microM). The pretreatment study demonstrated an antiviral effect that lasted 100 days after a single intravitreal injection.

CONCLUSIONS

This crystalline lipid prodrug intravitreal delivery system is an effective approach to achieving sustained, therapeutic drug levels in the eye. Small microfluidized particles of HDP-P-GCV provide more rapid dissolution and higher vitreous drug levels.

Improved insulin sensitivity in hyperinsulinaemic ponies through physical conditioning and controlled feed intake

Ten hyperinsulinaemic ponies divided into conditioned (N = 5) and rested (N = 5) groups were evaluated for their insulin and glucose response following oral glucose administration at Weeks 0, 2, 4, and 6. All ponies received a controlled intake of a pelleted ration during the study. In both groups body weight had decreased from baseline by Week 4 and remained low. After 2 weeks of exercise, ponies in the conditioned group had significantly decreased insulin and glucose indices, including peak insulin response, area under the insulin curve from 0 to 210 min (TIS), and the TIS value: area under the glucose curve from 0 to 210 min. By Week 4 of conditioning, although the insulin and glucose indices continued to decrease in the exercised ponies, there was no significant difference between the groups. Over the first 6 weeks of the study all ponies improved their insulin sensitivity accompanied by a loss of body weight. The conditioned ponies were further evaluated during deconditioning at Weeks 8, 10 and 12. The improved insulin sensitivity was maintained during deconditioning.

Measurement of oxygen uptake in the non-steady-state

The purpose of these experiments was to develop and validate an open-circuit technique for measurement of gas exchange during the transition from rest to constant load steady-state exercise. The design of the open-circuit system employed to measure gas exchange in these experiments used a mixing chamber to collect the subject's expired ventilation where fractions of O2 and CO2 were determined via electronic gas analyzers. A gasometer was used to measure inspired ventilation and the analog signals from the two gas analyzers and the gasometer were sent to a microcomputer for computation of VO2. In calculating VO2, the mixed expired gas concentrations were matched with ventilatory volume using a previously determined time delay. To determine the validity of the open-circuit system, four subjects performed a series of 16 rest-to-work transitions on a cycle ergometer. In eight of the experiments, serial measurements of VO2 were obtained every 20 s for 3 min using the open-circuit mixing chamber system while the additional eight experiments used the Douglas bag technique. No significant difference (p greater than 0.05) existed between VO2 values calculated by the two techniques. Mean differences in VO2 between the two techniques during the first three 20-s measurement periods were 6, 53, and 63 ml, respectively. Using the Douglas bag technique as the standard, this represents a relative measurement error of 0.1%, 4.5%, and 3.6%, respectively, at the above time intervals. These data demonstrate that an open-circuit system employing a mixing chamber and the appropriate time delay to match expired gas fractions and ventilation is a sensitive means of measurement of VO2 in the non-steady-state.

Ventral approach for stabilization of atlantoaxial subluxation secondary to odontoid fracture in a foal

Atlantoaxial subluxation secondary to odontoid fracture in a 30-day-old foal was corrected by alignment of the atlantoaxial joint and stabilization with 2 ventrally placed dynamic compression plates. At 90 days after surgery, healing of the fracture, with adequate alignment of the atlantoaxial joint, was confirmed radiographically. The foal was only slightly tetraparetic at that time. At 1 year after surgery, the gait was normal. It was concluded that the technique has advantages over the use of Steinmann's pins or external coaptation for stabilization. The ventral approach allows decompression, anatomic alignment, and immediate stabilization of the subluxation. Potential complications of the ventral approach include laryngeal paralysis.

Aorticopulmonary septal defect in a dog

A 2-year-old Brittany Spaniel ahd clinical signs of pulmonary diseases and pulmonary hypertension, with cardiac murmur and congestive heart failure. Aorticopulmonary septal defect was detected by means of cardiac catheterization. Attempted surgical correciton was unsuccessful.