Left Ventricular Posterior Papillary Muscle Research Articles

Long-term study on electrophysiological characteristics and catheter ablation of idiopathic ventricular arrhythmias originating from the left ventricular posterior papillary muscles guided by intracardiac ultrasound.

BackgroundThis study aimed to investigate the electrophysiological characteristics of idiopathic ventricular arrhythmias (VAs) originating from the left ventricular posterior papillary muscles (LPPM) and explore the efficiency of catheter ablation using three‐dimensional intracardiac ultrasound technology.MethodsTwenty‐seven cases of premature ventricular contraction/ventricular tachycardia (PVC/VT) originating from the left ventricular posterior papillary muscles were recorded from July 2015 to June 2019 in the Central Hospital of Shengli Oil Field and the First Affiliated Hospital of Zhengzhou University. Electrophysiological mapping and radiofrequency catheter ablation (RFCA) were performed using three‐dimensional intracardiac ultrasound technology. The characteristics of the body surface and intracavity electrocardiogram were analyzed. All cases were followed up for 24 months after the operation.ResultsThe VAs of all 27 cases were successfully eliminated by catheter ablation. QRS complexes were observed with a right bundle branch block (RBBB) pattern and a steep slope in the initial segment. Lead I appeared with an Rs pattern, and inferior leads (lead II, III, and aVF) were usually with an S wave. The lead aVR appeared with a qR pattern, while the R wave was commonly found in aVL. The main wave in leads V1‐V3 was positive but negative in V5 and V6.ConclusionVentricular arrhythmias originating from the left ventricular posterior papillary muscles have similar electrophysiological characteristics. The origin site was accurately located using three‐dimensional intracardiac ultrasound technology. Catheter ablation effectively eliminated VAs.

Remote magnetic-guided ablation for three origins of idiopathic ventricular arrhythmias with right bundle branch block and superior axis.

BackgroundIdiopathic ventricular arrhythmias (IVAs) with right bundle branch block (RBBB) and superior axis commonly originate from posterior mitral annulus (PMA), the left ventricular (LV) posterior fascicle (LPF), and the LV posterior papillary muscles (PPM).HypothesisRemote magnetic navigation (RMN)‐guided ablation might be safe and effective for these three origins of IVAs.MethodsThirty consecutive IVA patients with RBBB and superior axis (11 MPA‐IVAs, 11 LPF‐IVAs, and 8 PPM‐IVAs) were included in this study. Electrical mapping and ablation with RMN were performed in the LV through a trans‐septal approach. Navigation index, defined as the ratio of total radiofrequency (RF) time and the time from first burn to last burn, was used to determine the efficiency of RMN‐guided ablation.ResultsThe overall acute success rate was achieved in 93% (PMA, 100%; LPF, 91%; PPM, 88%; p > 0.05). No complication occurred in this study. The procedure time of PPM‐IVAs group was 34 and 14 min longer when compared with MPA‐IVAs and LPF‐IVAs group, respectively, without an increase of X‐ray time. The mean navigation index was 0.45 ± 0.20. The PPM‐IVAs group had an underperforming navigation index value (0.29 ± 0.11) (p < 0.01), as longer RF time was required in the PPM‐IVAs group.ConclusionsRMN‐guided ablation can achieve a high acute success rate for IVAs with RBBB and superior axis. The lower navigation index for PPM‐IVAs indicated that increasing the RF time and improving the catheter contact should be considered when using RMN.

Successful Bipolar Radiofrequency Catheter Ablation of Premature Ventricular Contractions Originating From the Left Ventricular Posterior Papillary Muscle

Successful Bipolar Radiofrequency Catheter Ablation of Premature Ventricular Contractions Originating From the Left Ventricular Posterior Papillary Muscle

A Case of Sustained Ventricular Tachycardia Originated from Left Ventricular Posterior Papillary Muscle, Which Was Misinterpreted as Posterior Fascicular Ventricular Tachycardia in ECG Morphology

A case was 18 years old male who complained of severe palpitation. 12 lead ECG showed sustained ventricular tachycardia (VT) rate 180 beat per minute with left axis deviation and right bundle branch block. Verapamil was effective to terminate the arrhythmia. As suntained VT was not induced in catheter laboratory, we misdiagnosed as posterior fascicular VT from etiological prevalence and pharmacological behavior at first. With CARTO system we found Purkinje potential with location information, and then RF energy applied at the distal site with Purkinje potential. After several RF delivered, we thought the ablation as unsuccessful from reasons of imperfect pacemap and inducibility of non-sustained VT. By re-mapping in left ventricule and observating CARTO image, we had good pace mapping at posterior papillary muscle near the former ablation site. As Successful ablation with heating effect, we conclude that VT arose from posterior papillary muscle. In this case, 12 lead ECG characteristics were not enough to differentiate these arrhythmias which had other origins. So we had to rule out these arrhythmias to correct diagnosis and therapy.

Successful catheter ablation of a ventricular tachycardia storm originating from the left ventricular posterior papillary muscle involved with a remote myocardial infarction

A 61-year-old man with a remote posterior myocardial infarction underwent electrophysiological testing for a ventricular tachycardia (VT) storm. Repeated cardioversions terminated the VT with immediate resumption after one sinus beat. Pacing neither terminated the VT nor demonstrated transient entrainment. Echocardiographically guided electroanatomic mapping revealed a centrifugal activation from the septal mid-apical region of the left ventricle on the septal portion of the posterior papillary muscle where a high frequency potential was observed within the local ventricular electrogram. Irrigated radiofrequency current at this site eliminated the VT. This case suggested that papillary muscles may be a target for catheter ablation of electrical storms after myocardial infarctions.

Effects of metoprolol and ramipril on action potentials after myocardial infarction in rats

The effects of chronic treatment with the β-adrenoceptor antagonist metoprolol, the angiotensin converting enzyme inhibitor ramipril, their combination, or placebo on action potential configuration 6 weeks after myocardial infarction in rats were studied. Action potentials were measured in isolated left ventricular posterior papillary muscles and compared with action potentials from a sham operated group without infarction. After infarction, the action potential amplitude was reduced and this phenomenon was partially reversed by metoprolol- and ramipril-treatment. Prolonged repolarisation after infarction compared to sham operated animals was additionally delayed after metoprolol treatment. Thus, metoprolol extends the refractory period, which may counteract tachyarrhythmia.

Inhibition of rat cardiac muscle contraction and mitochondrial respiration by endogenous peroxynitrite formation during posthypoxic reoxygenation.

This study was designed to investigate the potential role of endogenous peroxynitrite (ONOO-) formation in the inhibition of cardiac muscle contractility and mitochondrial respiration during posthypoxic reoxygenation. Isometric contraction of isolated rat left ventricular posterior papillary muscle was virtually eliminated at the end of an exposure to 15 minutes of hypoxia and remained 40+/-5% depressed an hour after the reintroduction of O2. O2 uptake by rat left ventricular cardiac muscle, measured by a Clark-type O2 electrode, was also inhibited by 24+/-2% at 10 minutes after reoxygenation. The inhibition of contractility and respiration during posthypoxic reoxygenation was markedly attenuated by the NO synthase inhibitor nitro-L-arginine, exogenous superoxide dismutase, and the ONOO- scavenger urate but not by the hydroxyl radical scavenger mannitol. Generation of ONOO- with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) plus the superoxide-releasing agent pyrogallol caused an irreversible inhibition of cardiac contractile and respiratory function. Unlike ONOO-, exogenous (SNAP) and endogenous (bradykinin) sources of NO inhibited contractility in a reversible manner. Under conditions of comparable amounts of respiratory inhibition in unstimulated incubated muscle, the NO-dependent agents and the mitochondrial antagonist NaCN produced a smaller degree of suppression of contractility compared with ONOO- and posthypoxic reoxygenation. These results are consistent with a contributing role for endogenous ONOO- formation in the inhibition of cardiac muscle contractility and mitochondrial respiration during posthypoxic reoxygenation.

Extensive cryoablation of the left ventricular posterior papillary muscle and subjacent ventricular wall: Impact on mitral valve function and hemodynamics

Ventricular tachycardias that originate from the inferior left ventricular wall may necessitate transmural ablation involving the posterior papillary muscle of the mitral valve. The effect on mitral valve function and hemodynamics of extensive cryoablation of the left ventricular posterior papillary muscle and subjacent ventricular wall was studied in 16 dogs. Two sham experiments were done. All dogs were studied preoperatively and postoperatively by pulsed Doppler and two-dimensional echocardiography. Left ventricular angiographic and hemodynamic studies were performed preoperatively in six treated dogs and two control dogs and in all dogs at the end of follow-up (1, 3, or 6 months). Postmortem studies were performed in all dogs. The cumulative probability of freedom from mitral regurgitation at 2 months was 0.43 +/- 0.14. Thereafter no new cases of mitral regurgitation could be demonstrated. The angiographic degree of mitral regurgitation was mild in five and moderate in two dogs and did not increase from 3 to 6 months. One dog with acute severe mitral regurgitation died early of heart failure. A significant increase in left ventricular end-diastolic and mean pulmonary capillary wedge pressure of 9.4 +/- 2.5 mm Hg and 6.4 +/- 2.6 mm Hg, respectively, was found in treated dogs at 3 months. These results suggest that extensive cryoablation of the left ventricular posterior papillary muscle and subjacent ventricular wall can be accomplished with an acceptable risk of mild to moderate mitral regurgitation, and without serious detrimental effect on left ventricular function. Retraction is probably the main mechanism of mitral regurgitation.

Myocardial mechanics predict hemodynamic performance during normal function and alcohol-induced dysfunction in rats

To determine whether mechanical evaluation of muscle tissue removed from the myocardium can be employed as a direct indicator of cardiac contractile performance in situ, isometric and isotonic parameters of muscle mechanics in vitro were correlated with in vivo global functional characteristics of the same heart. Twelve-month-old animals maintained on standard food and water were employed as representative of normal cardiac function. Animals of identical age with left ventricular (LV) dysfunction induced by oral alcohol (30%) ingestion from 4 to 12 mo were utilized to represent depressed cardiac performance. Accordingly, 24 h after the establishment of the hemodynamic profile for a control or experimental heart, the LV posterior papillary muscle was removed from the same heart and examined isometrically and isotonically. Least squares regression analysis was employed to establish a correlation coefficient and P values between various in vitro and in vivo parameters. Hemodynamic measurements were performed under chloral hydrate anesthesia and LV pump performance was evaluated with respect to aortic and ventricular pressures and the rates of rise and decay of the LV pressure trace. Papillary muscles were evaluated with respect to timing parameters of the isometric and isotonic twitch, the first derivative of isometric tension development, and the speed of muscle shortening at increasing physiologic loads. LV peak rate of pressure rise and decay were then correlated with the various isometric and isotonic properties. Myocardial mechanics and hemodynamics revealed depressed function in the papillary muscles and hearts from alcoholic rats. Moreover, significant correlations were found between the LV rate of pressure change (peak +dP/dt and -dP/dt) and both isometric and isotonic twitch measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanical and electrical properties of cardiomyopathic hearts of Syrian hamsters.

To determine whether the cardiomyopathy that develops in the Syrian hamster before the occurrence of congestive heart failure is associated with mechanical and electrical alterations consistent with myocardial dysfunction, left ventricular posterior papillary muscles of control and cardiomyopathic animals at 120 days of age were studied in vitro. Moreover, the electrocardiographic response to ouabain was investigated in vivo to analyze the arrhythmogenic potential of the cardiomyopathic heart to glycoside exposure. Results showed a decreased tension-generating ability of the myocardium in the diseased animals, which was accompanied by a prolongation of the timing parameters of contraction and an increase in the duration of the repolarization phase of the transmembrane action potential. Furthermore, the velocity of isotonic muscle shortening and relengthening was depressed at all physiological loads. Glycoside infusion elicited premature ventricular contractions, ventricular tachycardia, and ventricular fibrillation in diseased hamsters much earlier in time than in healthy controls. The impairment in mechanical performance in association with the abnormality in membrane electrical activity may be responsible for the progression of the disease process and the occurrence of lethal arrhythmias in this animal model.

Mitral valve function after cryoablation of the posterior papillary muscle in the dog

Extensive cryoablation of an arrhythmogenic left ventricular posterior papillary muscle associated with ventricular arrhythmias may affect mitral valve function. We studied the long-term effects of extensive cryoablation of the posterior papillary muscle and its ventricular attachment in 10 dogs. The dogs had hemodynamic, electrophysiological, and angiographic testing 1 month after operation. Seven dogs were then killed, and the hearts were examined at that time. Three dogs had repeat assessments 2 and 3 months after operation before they were killed. At 1 month, left ventricular angiography showed normal mitral valve function in all dogs. Pathological examination revealed that the posterior papillary muscle and its left ventricular attachment were replaced by a discrete dense, fibrous scar. The fibrous process involved the mitral valve in 2 dogs. At 3 months, pathological examination showed a marked fibrous scar with chondroid metaplasia and fibrous involvement of the mitral valve chordae and posterior leaflet in all 3 dogs. We conclude that extensive cryoablation of the posterior papillary muscle is not associated with long-term mitral valve dysfunction, and may be the best surgical technique to ablate an arrhythmogenic papillary muscle.

Morphometric observations on the rat heart after high-dose treatment with cortisol

Male Wistar rats were treated with high cortisol doses for 1 week. The dose administered daily was 15 mg per animal in group 1 (7 animals) and 30 mg in group 2 (7 animals). 7 rats served as control group. After cortisol treatment the body weights decreased due to skeletal muscle catabolism and the heart weights increased. Morphometric analysis of the left ventricular posterior papillary muscles gave evidence that the increased heart weights resulted from an increased number of mitochondria and an increased volume of the cytoplasm, whereas the myofibrillar mass was not affected. The surface area of inner mitochondrial membranes (+cristae mitochondriales) per myofibrillar unit volume increased from 15.7 μ2/μ3 to 21.3 μ2/μ3 in group 1 and 21.4 μ2/μ3 in group 2. Ultrastructural changes indicating myocardial cell damage were absent. Similar quantitative results have been reported to occur in the early phase of cardiac overload. For elucidating the hemodynamic effects of glucocorticoid a second experiment was performed: 7 Wistar rats were treated with cortisol in the same way as group 1, 7 others of the same body weight served as control. The systolic arterial pressure was significantly elevated in the cortisol group. Though myocardial tissue is known to be able to accumulate large quantities of glucocorticoids our results indicate that the application of high cortisol doses for a short time does not produce myocardial cell damage and does not suppress the myocardial adaption to the glucocorticoid-induced hypertension, i.e. hypertrophy. On the contrary, it seems to be possible that the adaption process is itself facilitated or accelerated by the presence of high cortisol concentrations in the heart. This thesis is supported by the considerably higher relative heart weights in the cortisol groups and is in agreement with observations reported by other authors.

An effective morphometric method for electron microscopic studies on papillary muscles.

Morphometry was performed on the left ventricular posterior papillary muscles of seven Wistar rats. The volume densities of myocardial cells, interstitial space, myocardial nuclei, sarcoplasm, mitochondria, myofibrils, ground substance and T tubules, and the surface densities of myocardial cells, mitochondrial membranes and T tubules, were calculated. Though only 1 ultrathin section per animal was evaluated the low standard errors of the means indicate that the method described here will be adequate in most experimental studies. Due to the anisotropy of the surfaces within myocardial cells, the papillary muscles were cut at an angle of 32.4 degrees to their longitudinal axis. This angle is derived from an equation published by Whitehouse (1974). The procedure to correct the loss of cristal membrane images from oblique sectioning is discussed.