Metabolic modulation and optimization of energy consumption in heart failure

Beyond Pressure Gradients: The Effects of Intervention on Heart Power in Aortic Coarctation

BACKGROUND

In aortic coarctation, current guidelines recommend reducing pressure gradients that exceed given thresholds. From a physiological standpoint this should ideally improve the energy expenditure of the heart and thus prevent long term organ damage.

OBJECTIVES

The aim was to assess the effects of interventional treatment on external and internal heart power (EHP, IHP) in patients with aortic coarctation and to explore the correlation of these parameters to pressure gradients obtained from heart catheterization.

METHODS

In a collective of 52 patients with aortic coarctation 25 patients received stenting and/or balloon angioplasty, and 20 patients underwent MRI before and after an interventional treatment procedure. EHP and IHP were computed based on catheterization and MRI measurements. Along with the power efficiency these were combined in a cardiac energy profile.

RESULTS

By intervention, the catheter gradient was significantly reduced from 21.8±9.4 to 6.2±6.1mmHg (p<0.001). IHP was significantly reduced after intervention, from 8.03±5.2 to 4.37±2.13W (p < 0.001). EHP was 1.1±0.3 W before and 1.0±0.3W after intervention, p = 0.044. In patients initially presenting with IHP above 5W intervention resulted in a significant reduction in IHP from 10.99±4.74 W to 4.94±2.45W (p<0.001), and a subsequent increase in power efficiency from 14 to 26% (p = 0.005). No significant changes in IHP, EHP or power efficiency were observed in patients initially presenting with IHP < 5W.

CONCLUSION

It was demonstrated that interventional treatment of coarctation resulted in a decrease in IHP. Pressure gradients, as the most widespread clinical parameters in coarctation, did not show any correlation to changes in EHP or IHP. This raises the question of whether they should be the main focus in coarctation interventions. Only patients with high IHP of above 5W showed improvement in IHP and power efficiency after the treatment procedure.

TRIAL REGISTRATION

clinicaltrials.gov NCT02591940.

Efficacy and Safety of a Metabolic Modulator Drug in Chronic Stable Angina: Review of Evidence from Clinical Trials

A number of newer antianginal agents, including nicorandil, trimetazidine, and ivabradine, have been synthesized in recent years, but ranolazine, a piperazine derivative that partially inhibits fatty acid oxidation and the late INa current in animal models, is of particular interest mechanistically. Earlier clinical trials with immediate-release ranolazine led to the current sustained-release version tested in the Monotherapy Assessment of Ranolazine In Stable Angina (MARISA) (n = 193) and Combination Assessment of Ranolazine In Stable Angina (CARISA) trials (n = 823) of patients with chronic angina and severe limitation of exercise capacity (ie, < 5 metabolic equivalents). MARISA was a placebo-controlled, randomized trial that compared ranolazine monotherapy (500 mg, 1000 mg, and 1500 mg, twice daily) to placebo. CARISA was a placebo-controlled trial that randomized patients on background 1-blocker or calcium antagonist therapy to placebo or ranolazine (750 mg or 1000 mg, twice daily). Both studies showed a significant increase in total exercise duration, time to angina onset, and time to 1 mm ST segment depression. The average magnitude of increase in exercise duration over placebo was 29 to 56 seconds at peak and 24 to 46 seconds at trough with the 3 doses tested in MARISA, and 24 to 34 seconds greater than placebo with the 2 doses used in CARISA. The beneficial effect was achieved without clinically important changes in rest or exercise heart rate or blood pressure. Weekly angina attack frequency and nitroglycerin usage were significantly reduced in a dose-dependent manner in the 12-week CARISA trial. Reported adverse effects were similar in MARISA and CARISA and consisted of asthenia, nausea, constipation, and dizziness. Syncope, reported in 8 patients at doses of 1000 mg twice daily or more may be related to attenuation of α-1 receptor activity. The mean QTc interval increased with dose and was less than 10 msec on ranolazine at 1000 mg twice daily. The mortality rates at 1 and 2 years in MARISA and CARISA open-label run-on studies were 2% and less than 5%, acceptable for this high-risk population with limited exercise capacity. In conclusion, clinical trial evidence with ranolazine to date is consistent with its proposed mechanism of action and demonstrates an effective antianginal profile that may benefit patients with severe chronic angina.

The bone mass (BM) and chronic cardiac decompensation (CCD) in an elderly population

This study intended to evaluate the existing correlation between the cardiac compensation and the bone mass, investigating the bone mineral density (BMD) in a population suffering from CCD or chronic heart disease (CHD). We enrolled 171 patients, all over the age of 70, being in the functional N.Y.H.A. Class II (Population A: 85 patients) and in Class III (Population B: 86 patients). All patients underwent an analysis of their cardiac functions using a Doppler echo-cardiographic method measuring the ventricular ejection fraction (VEF), as well as the BMD by means of a computerized bone mineralometric DEXA method, performed in vertebral and femoral measurement sites. Both populations proved to be osteopenic, displaying reduced values of BMD. Higher bone mineral losses were measured in the patients who had more severe cardiac insufficiency. The present data revealed a significant reduction of BMD in the N.Y.H.A. Class III patients, in correlation with the VEF (p<0.001), both in the lumbar vertebral area (p<0.01) and even more in the femoral sites (p<0.001), where a direct correlation exists between BMD and the VEF. On the basis of these findings one can suggest that the actual VEF level has an influence on the bone turnover, reducing the mineral content through various mechanisms of action.

Treating Chronic Fatigue states as a disease of the regulation of energy metabolism

Chronic Fatigue Syndrome is a physiological state in which the patient feels high levels of fatigue without an obvious organic cause, which affects around 1 in 400 people in the developed world. A wide range of causes have been suggested, including immune or hormonal dysfunction, viral or bacterial infection, and psychological somatization. It is likely that several causes are needed to trigger the disease, and that the triggers are different from the mechanisms that maintain fatigue over months or years. Many treatments have been tested for CFS, with very limited success - a programme of combined CBT and graded exercise shows the most effect. I suggest that patients with CFS have a reduced ability to increase mitochondrial energy production when exertion requires it, with fewer mitochondria that are each more efficient, and hence nearer to their maximum energy output, than normal. A range of indirect evidence suggests that the renin-angiotensin system stimulates mitochondrial responsiveness and reduces mitochondrial efficiency: chronic under-stimulation of this system could contribute to CFS aetiology. If correct, this means that CFS can be successfully treated with RAS agonists (eg angiotensin mimetics), or adrenergic agonists. It also suggests that there will be a positive link between the use of adrenergic- and RAS-blocking drugs and CFS incidence, and a negative link between adrenergic agonist use and CFS.

Structural and functional remodeling of the left atrium: clinical and therapeutic implications for atrial fibrillation

Left atrial (LA) structural and functional remodeling reflects a spectrum of pathophysiological changes that have occurred in response to specific stressors. These changes include alterations at the levels of ionic channels, cellular energy balance, neurohormonal expression, inflammatory response, and physiologic adaptations. There is convincing evidence demonstrating an important pathophysiological association between LA remodeling and atrial fibrillation (AF). Measures that will prevent, attenuate, or halt these processes of LA remodeling may have a major public health impact with respect to the epidemic of AF. In this review, we describe the mechanisms involved in LA remodeling and highlight the existing and potential therapeutic options for its reversal, and implications for AF development.

Ranolazine: ion-channel-blocking actions and in vivo electrophysiological effects

Ranolazine is a novel anti-ischemic drug that prolongs the QT interval. To evaluate the potential mechanisms and consequences, we studied: (i) Ranolazine's effects on HERG and IsK currents in Xenopus oocytes with two-electrode voltage clamp; (ii) effects of ranolazine, compared to d-sotalol, on effective refractory period (ERP), QT interval and ventricular rhythm in a dog model of acquired long QT syndrome; and (iii) effects on selected native currents in canine atrial myocytes with whole-cell patch-clamp technique. Ranolazine inhibited HERG and IsK currents with different potencies. HERG was inhibited with an IC(50) of 106 micromol l(-1), whereas the IC(50) for IsK was 1.7 mmol l(-1). d-Sotalol caused reverse use-dependent ERP and QT interval prolongation, whereas ranolazine produced modest, nonsignificant increases that plateaued at submaximal doses. Neither drug affected QRS duration. d-Sotalol had clear proarrhythmic effects, with all d-sotalol-treated dogs developing torsades de pointes (TdP) ventricular tachyarrhythmias, of which they ultimately died. In contrast, ranolazine did not generate TdP. Effects on I(Kr) and I(Ks) were similar to those on HERG and IsK. Ranolazine blocked I(Ca) with an IC(50) of approximately 300 micromol l(-1). I(Na) was unaffected. We conclude that ranolazine inhibits I(Kr) by blocking HERG currents, inhibits I(Ca) at slightly larger concentrations, and has modest and self-limited effects on the QT interval. Unlike d-sotalol, ranolazine does not cause TdP in a dog model. The greater safety of ranolazine may be due to its ability to inhibit I(Ca) at concentrations only slightly larger than those that inhibit I(Kr), thus producing offsetting effects on repolarization.