New treatment methods for patients with hypertrophic obstructive cardiomyopathy

A modified endocardial radiofrequency ablation approach for hypertrophic obstructive cardiomyopathy guided by transthoracic echocardiography: a case series

Background

A series of studies showed that endocardial radiofrequency ablation (ERFA) could reduce the left ventricular outflow tract (LVOT) gradient in patients with septal hypertrophy. This study aimed to determine the safety and efficacy of a modified ERFA approach guided by transthoracic echocardiography (TTE) as an alternative to ablation performed under a three-dimensional (3D) electroanatomical system or intracardiac echocardiography (ICE).

Methods

Twenty-five patients with hypertrophic obstructive cardiomyopathy (HOCM) underwent ERFA of septal hypertrophy, guided by echocardiography. The LVOT gradient, left ventricular ejection fraction (LVEF), LV thickness, New York Heart Association (NYHA) class, and biochemical laboratory values were recorded before ablation and during follow-up.

Results

The patients’ peak and stress-induced LVOT gradients were significantly reduced after 12 months of follow-up (resting gradient: from 123.2±17.7 to 15.7±7.8 mmHg, P<0.05; provocative gradient: from 140.2±20.8 to 18.4±8.0 mmHg, P<0.05). Compared with baseline, the septal diameter was reduced slightly after 12 months, but the difference was not significant (24.8±3.5 vs. 24.2±3.4 mm, P>0.05). The reduction in LVOT gradient was associated with an improvement in NYHA functional classification (from 3.0±0.0 to 1.6±0.7, P<0.05), the 6-minute walking distance (413±129 m at baseline; 458±108 m immediately after ERFA; 471±139 m after 12 months, P<0.05), and pro B-type natriuretic peptide levels (from 924.00±139 to 137.45 ±75.73 pg/mL, P<0.05). After the procedure, the patients showed no worsening of LVEF compared with baseline (64%±5.3%), and no cases of bundle branch block nor complete heart block occurred.

Conclusions

ERFA guided by TTE provides a new treatment option for HOCM which can achieve symptomatic improvement as well as a significant and sustained reduction of the LVOT gradient. Moreover, by avoiding the use of the 3D electroanatomical system or ICE, this treatment has an acceptable cost.

Pacing for drug-refractory or drug-intolerant hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a genetic disease with an autosomal-dominant inheritance for which negative inotropes are the most widely used initial therapies. Observational studies and small randomised trials have suggested symptomatic and functional benefits using pacing and several theories have been put forward to explain why. Pacing, although not the primary treatment for HCM, could be beneficial to patients with relative or absolute contraindications to surgery or alcohol ablation. Several randomised controlled trials comparing pacing to other therapeutic modalities have been conducted but no Cochrane-style systematic review has been done.

OBJECTIVES

To assess the effects of pacing in drug-refractory or drug-intolerant hypertrophic cardiomyopathy patients.

SEARCH METHODS

We searched the following on the 14/4/2010: CENTRAL (The Cochrane Library 2010, Issue 1), MEDLINE OVID (from 1950 onwards ), EMBASE OVID (from 1980 onwards ), Web of Science with Conference Proceedings (from 1970 onwards). No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled trials of either parallel or crossover design that assess the beneficial and harmful effects of pacing for hypertrophic cardiomyopathy were included. When crossover studies were identified, we considered data only from the first phase.

DATA COLLECTION AND ANALYSIS

Data from included studies were extracted onto a pre-formed data extraction paper by two authors independently. Data was then entered into Review Manager 5.1 for analysis. Risk of bias was assessed using the guidance provided in the Cochrane Handbook. For dichotomous data, relative risk was calculated; and for continuous data, the mean differences were calculated. Where appropriate data were available, meta-analysis was performed. Where meta-analysis was not possible, a narrative synthesis was written. A QUROUM flow chart was provided to show the flow of papers.

MAIN RESULTS

Five studies (reported in 10 papers) were identified. However, three of the five studies provided un-usable data. Thus the data from only two studies (reported in seven papers) with 105 participants were included for this review. There was insufficient data to compare results on all-cause mortality, cost effectiveness, exercise capacity, Quality of life and Peak O2 consumption.When comparing active pacing versus placebo pacing on exercise capacity, one study showed that exercise time decreased from (13.1 ± 4.4) minutes to (12.6 ± 4.3) minutes in the placebo group and increased from (12.1 ± 5.6) minutes to (12.9 ± 4.2) minutes in the treatment group (MD 0.30; 95% CI -1.54 to 2.14). Statistically significant data from the same study showed that left ventricular outflow tract obstruction decreased from (71 ± 32) mm Hg to (52 ± 34) mm Hg in the placebo group and from (70 ± 24) mm Hg to (33 ± 27) mm Hg in the active pacing group (MD -19.00; 95% CI -32.29 to -5.71). This study was also able to show that New York Heart Association (NYHA) functional class decreased from (2.5 ± 0.5) to (2.2 ± 0.6) in the inactive pacing group and decreased from (2.6 ± 0.5) to (1.7 ± 0.7) in the placebo group (MD -0.50; 95% CI -0.78 to -0.22).When comparing active pacing versus trancoronary ablation of septal hypertrophy (TASH), data from one study showed that NYHA functional class decreased from (3.2 ± 0.7) to (1.5 ± 0.5) in the TASH group and decreased from (3.0 ± 0.1) to (1.9 ± 0.6) in the pacemaker group. This study also showed that LV wall thickness remained unchanged in the active pacing group compared to reduction from (22 ± 4) mm to (17 ± 3) mm in the TASH group (MD 0.60; 95% CI -5.65 to 6.85) and that LV outflow tract obstruction decreased from (80 ± 35.5) mm Hg in the TASH group to (49.3 ± 37.7) mm Hg in the pacemaker group.

AUTHORS' CONCLUSIONS

Trials published to date lack information on clinically relevant end-points. Existing data is derived from small trials at high risk of bias, which concentrate on physiological measures. Their results are inconclusive. Further large and high quality trials with more appropriate outcomes are warranted.

Quantification of cardiovascular biomarkers in patient plasma by targeted mass spectrometry and stable isotope dilution

Verification of candidate biomarkers requires specific assays to selectively detect and quantify target proteins in accessible biofluids. The primary objective of verification is to screen potential biomarkers to ensure that only the highest quality candidates from the discovery phase are taken forward into preclinical validation. Because antibody reagents for a clinical grade immunoassay often exist for a small number of candidates, alternative methodologies are required to credential new and unproven candidates in a statistically viable number of serum or plasma samples. Using multiple reaction monitoring coupled with stable isotope dilution MS, we developed quantitative, multiplexed assays in plasma for six proteins of clinical relevance to cardiac injury. The process described does not require antibodies for immunoaffinity enrichment of either proteins or peptides. Limits of detection and quantitation for each signature peptide used as surrogates for the target proteins were determined by the method of standard addition using synthetic peptides and plasma from a healthy donor. Limits of quantitation ranged from 2 to 15 ng/ml for most of the target proteins. Quantitative measurements were obtained for one to two signature peptides derived from each target protein, including low abundance protein markers of cardiac injury in the nanogram/milliliter range such as the cardiac troponins. Intra- and interassay coefficients of variation were predominantly <10 and 25%, respectively. The configured multiplex assay was then used to measure levels of these proteins across three time points in six patients undergoing alcohol septal ablation for hypertrophic obstructive cardiomyopathy. These results are the first demonstration of a multiplexed, MS-based assay for detection and quantification of changes in concentration of proteins associated with cardiac injury in the low nanogram/milliliter range. Our results also demonstrate that these assays retain the necessary precision, reproducibility, and sensitivity to be applied to novel and uncharacterized candidate biomarkers for verification of proteins in blood.

A novel minimal-invasive model of chronic myocardial infarction in swine

BACKGROUND

Most animal studies on myocardial infarction (MI) have used open-chest models with direct surgical coronary artery ligation, which imply local as well as generalized side effects of major surgery. Some closed-chest models of MI have been established, mainly using catheterization techniques with coronary artery embolization, balloon occlusion, and intracoronary injection of thrombogenic agents. The aim of this study was to develop a closed-chest technique of chronic coronary artery occlusion at a selected location with subsequent thrombus formation without use of balloon inflation or thrombotic chemical agents.

METHODS AND RESULTS

A coronary angiography via the carotid artery was performed using a 7 F guiding catheter in 21 pigs. After insertion of a percutaneous transluminal coronary angioplasty (PTCA) guide wire into the distal coronary artery, a vessel-size adapted flexible foreign body comprising an open-cell sponge was advanced into the coronary artery via the guide wire by a non-inflated PTCA balloon. Five min after removal of the guide wire and the balloon catheter, total coronary artery occlusion was documented by angiography. Retrograde thrombosis of the coronary artery occurred in three animals. After one week, total vessel occlusion at the previously selected location was visualized by coronary angiography in animals that had survived. Macroscopic analysis demonstrated the foreign body with subsequent thrombus formation in the coronary artery and distal MI. Post-mortem histological analysis revealed myocardial necrosis and granulocyte infiltration at the margin of the infarction, without damage to remote myocardium.

CONCLUSIONS

This new easy-to-perform closed-chest technique provides reproducible chronic coronary artery occlusion at a selected location with subsequent MI. It avoids major surgery and thoracotomy and does not require balloon inflation or intracoronary injection of thrombotic or chemical agents.

Transcoronary ablation of septal hypertrophy does not alter ICD intervention rates in high risk patients with hypertrophic obstructive cardiomyopathy

INTRODUCTION

Transcoronary ablation of septal hypertrophy (TASH) is safe and effectively reduces the intraventricular gradient in patients with hypertrophic obstructive cardiomyopathy (HOCM). To analyze the potential of anti- and proarrhythmic effects of TASH, we studied the discharge rates of implanted cardioverter defibrillators (ICD) in patients with HOCM who are at a high risk for sudden cardiac death.

METHODS

ICD and TASH were performed in 15 patients. Indications for ICD-implantation were secondary prevention in nine patients after resuscitation from cardiac arrest with documented ventricular fibrillation (n = 7) or sustained ventricular tachycardia (n = 2) and primary prevention in 6 patients with a family history of sudden deaths, nonsustained ventricular tachycardia, and/or syncope. All the patients had severe symptoms due to HOCM (NYHA functional class = 2.9).

RESULTS

During a mean follow-up time of 41 +/- 22.7 months following the TASH procedure, 4 patients had episodes of appropriate discharges (8% per year). The discharge rate in the secondary prevention group was 10% per year and 5% in the group with primary prophylactic implants. Three patients died during follow-up (one each of pulmonary embolism, stroke, and sudden death).

CONCLUSION

In conclusion, on the basis of ICD-discharge rates in HOCM-patients at high risk for sudden death, there is no evidence for an unfavorable arrhythmogenic effect of TASH. The efficacy of ICD treatment for the prevention of sudden cardiac death in HOCM could be confirmed, however, mortality is high in this cohort of hypertrophic cardiomyopathy patients.

Histological characterization of microlesions induced by myocardial contrast echocardiography

BACKGROUND

Myocardial contrast echocardiography (MCE) has been shown to have a potential for apparently reversible side effects related to the interaction of ultrasound with the contrast microbubbles, including premature ventricular contractions and microvascular leakage. We investigated the potential for high-dose MCE to induce histologically definable microlesions.

METHODS

Myocardial contrast echocardiography with 1:4 end-systolic triggering was performed at 1.5 MHz and 1.7 mechanical index in a short axis view of the left ventricle in rats. Two high doses (500 microl/kg) of Optison agent were given 5 minutes apart during 10 minutes of echocardiography. For histology, the hearts were perfused and fixed in 10% neutral-buffered formalin. Slides from rats sacrificed 1 day after MCE were scored blind by a pathologist, and, in addition, photomicrographs in the anterior half were evaluated by digital image analysis.

RESULTS

In rats sacrificed 10 minutes after MCE, microvascular leakage and petechiae were highly significant. However, lesions displaying necrotic debris associated with inflammatory infiltrates were not histologically evident at this time. Heart samples 24 hours after MCE showed microlesions with inflammatory infiltrates scattered primarily over the anterior half of the sections. Pathologically, there was inflammatory cell infiltration in areas of 0.6 +/- 0.5% for shams and 3.6 +/- 3.6% for MCE (P < 0.01). Analysis of photographs from the anterior wall found microlesion areas of 0.5 +/- 0.8% for shams and 7.4 +/- 5.0% for MCE (P < 0.02). For rats sacrificed 1 week and 6 weeks after MCE, the microlesions healed to form small fibrous regions interspersed with normal myocytes.

CONCLUSION

High-dose MCE has a potential for causing microscale lesions in the myocardium and the possibility of therapeutic applications.

[Therapeutic approaches in symptomatic hypertrophic obstructive cardiomyopathy]

Hypertrophic cardiomyopathy is a complex and heterogeneous disease. Although most patients experience just a few symptoms, and have a good prognosis, there are others whose symptoms are severe and progressive, determined by different pathophysiological elements such as diastolic dysfunction, myocardial ischemia, arrhythmias and subaortic obstruction. Approximately 20-30% of hypertrophic cardiomyopathy patients develop an intraventricular dynamic gradient, which in some cases, is responsible for severe symptoms which are ameliorated once the obstruction is reduced. In many cases the symptoms can be controlled with medical treatment which includes betablockers, calcium-channel antagonists and dysopiramide, but some patients will still experience severe and refractory symptoms. This subgroup of patients, which represent approximately 5-10% of patients with hypertrophic cardiomyopathy, can be problematic from a management perspective. For many years, septal myectomy and/or mitral valve replacement offered the only effective alternative therapy for these patients. However, the high rates of morbidity and mortality associated with these procedures have necessitated the search for new and less invasive procedures such as ventricular pacing and percutaneous septal ablation. Although the initial results with sequential pacing were encouraging, further studies have suggested a significant placebo effect, which makes its application controversial. In the last 5 years selective embolization of the septal artery precipitating a localized myocardial infarction has been utilized to reduce the subaortic gradient. The potential indications and efficacy of these new forms of treatment, like ventricular pacing and percutaneous septal ablation, are presently under evaluation and are the main subject of this review. Medical treatment, with either beta-blockers, calcium channel antagonists or dysopiramide constitutes the first therapeutic step. Surgery, while alleviating the subaortic obstruction and reducing the intraventicular pressure and mitral insufficiency, produces important and long-lasting symptomatic and functional improvement in most of these patients, and it continues to be an important therapeutic alternative in these cases. If the first results with sequential pacemaker implants were encouraging, today it is alluded to an important placebo effect that causes its application to be controversial. In the last 5 years the path has been made in the creation of a septal infarction located through the embolization of the septal branches to reduce the gradient.