Left Anterior Papillary Muscle Research Articles

High precision machine learning-enabled ECG algorithm for predicting sites of idiopathic ventricular arrhythmia origin

Abstract Introduction Radiofrequency catheter ablation (CA) is an efficient antiarrhythmic treatment with a class I indication for idiopathic ventricular arrhythmia (IVA). The accurate prediction of the origins of IVA can significantly increase the procedure success rate, reduce operation duration and decrease the risk of complications. The present work proposes an ECG analysis algorithm to estimate 21 possible origins of idiopathic ventricular arrhythmia at a clinical-grade level accuracy, which include left coronary cusp (LCC), right coronary cusp (RCC), aortomitral continuity (AMC), summit, LCC-RCC commissure, left His bundle, mitral valve (MV), left septal including left anterior fascicle (LAF), left posterior fascicle (LPF), left anterior papillary muscle (LAPM), left posterior papillary muscle (LPPM), anterior cusp (AC), left cusp (LC), right cusp (RC), RVOT septal, free wall, right His bundle, tricuspid valve (TV), and right anterior papillary muscle (RAPM). Method A total of 18,612 ECG recordings extracted from 545 patients who underwent successful CA to treat IVA were proportionally sampled into training, validation and testing cohorts. We designed four classification schemes responding to different hierarchical levels of the possible IVA origins. The first scheme will help the operators to figure out the origin from epicardium of left ventricular summit, right, and left ventricle. The second one can separate origins from left/right outflow tract and left/right non-out flow tract, respectively. The third one is able to predict 18 anatomical locations, and the fourth scheme can distinguish 21 possible sites. For every classification scheme, we compared 98 distinct machine learning models with optimized hyperparameter values obtained through extensive grid search and reported an optimal algorithm with the highest accuracy scores attained on the validation cohorts. Results In the first classification scheme used to predict right ventricular endocardium, left ventricular endocardium, and epicardium of left ventricular summit, the model achieved an accuracy of 99.79 (99.41–99.89) and a F1-score of 99.84 (99.6–99.96). For scheme 2, the proposed method reached an accuracy of 99.62 (99.09–99.78) and a F1-score of 99.42 (98.79–99.75). For scheme 3, the model achieved an accuracy of 97.78 (96.76–98.41), a F1-score of 97.74 (94.15–99.73), and an adjusted accuracy of 98.53 (98.33–99.15). For scheme 4 that can distinguish 21 origin sites, the proposed model attained an accuracy of 98.24 (97.36–98.71), a F1-score of 98.56 (97.88–99.12) and an adjusted accuracy of 98.75 (98.35–99.38). Conclusion The proposed machine learning model can be immediately and effortlessly deployed to electrophysiology labs allowing cardiologists to predict the exact origins of arrhythmia and provide an optimum treatment plan both before and during the CA procedure. This approach will significantly reduce the CA procedure duration and the risk of complications. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): 2020 Natural Science Foundation of Zhengjiang Province Confusion matrix for classification schemes

Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice.

Papillary muscle isolated from adult mouse hearts can be used to study cardiac contractility during different physiological/pathological conditions. The contractile characteristics can be evaluated independently of external influences such as vascular tonus or neurohumoral status. It depicts a scientific approach between single cell measurements with isolated cardiac myocytes and in vivo studies like echocardiography. Thus, papillary muscle preparations serve as an excellent model to study cardiac physiology/pathophysiology and can be used for investigations like the modulation by pharmacological agents or the exploration of transgenic animal models. Here, we describe a method of isolating the murine left anterior papillary muscle to investigate cardiac contractility in an organ bath setup. In contrast to a muscle strip preparation isolated from the ventricular wall, the papillary muscle can be prepared in toto without damaging the muscle tissue severely. The organ bath setup consists of several temperature-controlled, gassed and electrode-equipped organ bath chambers. The isolated papillary muscle is fixed in the organ bath chamber and electrically stimulated. The evoked twitch force is recorded using a pressure transducer and parameters such as twitch force amplitude and twitch kinetics are analyzed. Different experimental protocols can be performed to investigate the calcium- and frequency-dependent contractility as well as dose-response curves of contractile agents such as catecholamines or other pharmaceuticals. Additionally, pathologic conditions like acute ischemia can be simulated.

Anomalous Anterior Papillary Muscle as an Autopsy Finding in Two Cases

Anomaly in the anterior papillary muscle (APM) is known to cause left ventricle outflow tract (LVOT) obstruction, and this rare congenital condition could be a cause of sudden cardiac death. This anomaly and its hemodynamic effects is similar to valvular heart disease. In our two described cases, in which cause of death was, respectively, hypertrophic cardiomyopathy and suicide by hanging, the cephalad portion of the left APM was inserted directly into the ventricular surface of the anterior mitral leaflet and chordae tendineae were absent in the area of the direct anomalous muscle insertion; the aberrant papillary muscle was very large and showed an exaggerated anterior displacement within the left ventricular cavity. The described anomaly is a cause of LVOT obstruction. This condition is considered to be rare, although incidence estimates do not exist. In the absence of other possible causes, this finding may indicate arrhythmia as being the immediate cause of death.

Three‐Dimensional Electroanatomical Mapping‐Guided Catheter Ablation of Ventricular Tachycardia Originating in the Left Anterior Papillary Muscle

A 76-year-old man with a history of healed inferior myocardial infarction was admitted to our hospital for catheter ablation of ventricular tachycardia (VT) causing disabling palpitation. The 12-lead electrocardiogram (ECG) recorded during VT showed a QRS with right bundle branch block morphology and right axis deviation, consistent with an anterolateral left ventricular (LV) origin (Fig. 1A). Cardiac computed tomographic (CT) scans were obtained 1 day before the procedure, using a LightSpeed VCT 64-slice mul-

Chemical ablation of the Purkinje system causes early termination and activation rate slowing of long-duration ventricular fibrillation in dogs

Endocardial mapping has suggested that Purkinje fibers may play a role in the maintenance of long-duration ventricular fibrillation (LDVF). To determine the influence of Purkinje fibers on LDVF, we chemically ablated the Purkinje system with Lugol solution and recorded endocardial and transmural activation during LDVF. Dog hearts were isolated and perfused, and the ventricular endocardium was exposed and treated with Lugol solution (n = 6) or normal Tyrode solution as a control (n = 6). The left anterior papillary muscle endocardium was mapped with a 504-electrode (21 x 24) plaque with electrodes spaced 1 mm apart. Transmural activation was recorded with a six-electrode plunge needle on each side of the plaque. Ventricular fibrillation (VF) was induced, and perfusion was halted. LDVF spontaneously terminated sooner in Lugol-ablated hearts than in control hearts (4.9 +/- 1.5 vs. 9.2 +/- 3.2 min, P = 0.01). After termination of VF, both the control and Lugol hearts were typically excitable, but only short episodes of VF could be reinduced. Endocardial activation rates were similar during the first 2 min of LDVF for Lugol-ablated and control hearts but were significantly slower in Lugol hearts by 3 min. In control hearts, the endocardium activated more rapidly than the epicardium after 4 min of LDVF with wave fronts propagating most often from the endocardium to epicardium. No difference in transmural activation rate or wave front direction was observed in Lugol hearts. Ablation of the subendocardium hastens VF spontaneous termination and alters VF activation sequences, suggesting that Purkinje fibers are important in the maintenance of LDVF.

Catheter ablation of ventricular fibrillation in rabbit ventricles treated with beta-blockers.

A therapeutic implication of the focal-source hypothesis of ventricular fibrillation (VF) is that VF can be terminated by focal ablation. We hypothesize that beta-adrenergic receptor blockade converts multiple-wavelet VF to focal-source VF and that this focal source is located near the papillary muscle (PM). We used optical mapping techniques to study the effects of propranolol (0.3 mg/L) on VF dynamics in Langendorff-perfused rabbit hearts. The left ventricular (LV) anterior wall was mapped and optical action potential duration restitution (APDR) was determined at 25 epicardial sites. We performed ablation during VF of the left anterior PM in hearts with (N=6) or without (N=6) cytochalasin infusion, the LV lateral epicardium (Epi group, N=3), and the LV endocardium (Endo group, N=3). The PM was also ablated in 3 hearts without propranolol (control group). Propranolol converted multiple-wavelet VF to slow VF with reentry localized to the PM. Propranolol decreased the maximal slope of the APDR curve (P<0.001) as well as its spatial heterogeneity (P<0.01) and conduction velocity (P=0.01) while increasing the VF cycle length (P<0.001). PM ablation terminated VF during propropranolol infusion with (6 of 6, 100%) or without (4 of 6, 67%) cytochalasin D and significantly reduced inducibility. VF did not terminate in the Epi, Endo, and control groups (P<0.001). Propranolol flattens the APDR curve and reduces conduction velocity, converting multiple-wavelet VF into VF with a focal source anchored to the PM. Ablation of this focal source may terminate VF.

Left Ventricular Outflow Tract Obstruction in Atrioventricular Septal Defects: A Pathologic and Morphometric Evaluation

Subaortic stenosis has been described with increasing frequency as an ominous feature of atrioventricular septal defect (AVSD), especially following surgical correction of the anomaly in non-Down's syndrome patients. In order to study the surgical anatomy of the left ventricular outflow tract in this malformation, 48 hearts featuring AVSD were examined. Obstructive lesions were classified into unequivocal forms (class A, 13.5%) and potential ones (class B, 10.8%). In the remaining hearts (class C, 75.7%) no obstruction was noted. In class A, subaortic stenosis was due to exaggeration of the anticipated anomalous arrangement of atrioventricular valve tensor apparatus, to the persistence of a subaortic muscular infundibulum, and to a discrete fibrous diaphragm. A potential for subaortic stenosis is provided by the unwedged position of the aortic valve. The left ventricular outflow tract is transformed into a long, forward-displaced fibromuscular channel. Morphometric analysis showed in AVSD (with both common annulus and separate orifices) a significantly (p less than 0.01) lower inflow/outflow tract ratio, and a significantly (p less than 0.01) lower right ventricular/left ventricular outflow length ratio than normal hearts. These results suggest that AVSD is characterized not only, as commonly stated, by inflow tract shortening, but by outflow tract lengthening as well. On these anatomical grounds, nearly all cases of AVSD could harbor the potential for subaortic stenosis; however, this becomes a real hazard (class B) only when associated with forward displacement of the left anterior papillary muscle, or direct insertion on the ventricular septum of the anterior bridging leaflet, and it may be converted to an actual obstruction by the effects of surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

FUNCTIONAL UNIDIRECTIONAL BLOCK BETWEEN TWO LAYERS OF CARDIAC CONDUCTING TISSUE

Unidirectional block is a fundamental component in the initiation of a reentrant cardiac arrhythmia. The activation sequences of the adult rabbit (n=10) or canine (n=5) left anterior papillary muscle were mapped two-dimensionally using multiple monopolar extracellular electrodes with computerized data acquisition and analysis. Isochronal maps were then made to determine the activation patterns of the superficial Purkinje (P) layer or the underlying ventricular (V) layer during stimulation of an attached P strand or the apical V surface. The P cell layer extends over most of the surface of the left papillary muscle, but the direct propagation from the P layer into the underlying V layer is limited to several relatively discrete basal sites. We have additionally demonstrated sites located more apically which allow propagation in only one direction; namely, from the underlying V layer into the P layer. This phenomenon occurs because of a proposed resistive barrier between the two layers which is spatially inhomogeneous, with the junctional resistivity between the P and V layer increasing from base to apex. These sites of potential unidirectional conduction could have functional significance under abnormal conditions when the available sites of P-to-V conduction are reduced. This property could, therefore, operate as one of the mechanisms of cardiac reentrant arrhythmias.

Changes in the contractile state, fine structure and metabolism of cardiac muscle cells during the development of rigor mortis.

Transmural slices from the left anterior papillary muscle of dog hearts were maintained for 120 min in a moist atmosphere at 37 degrees C. At 15-min intervals tissue samples were taken for estimation of adenosine triphosphate (ATP) and glucose-6-phosphate (G6P) and for electron microscopic examination. At the same time the deformability under standard load of comparable regions of an adjacent slice of tissue was measured. ATP levels fell rapidly during the first 45 to 75 min after excision of the heart. During a subsequent further decline in ATP, the mean deformability of myocardium fell from 30 to 12% indicating the development of rigor mortis. Conversely, G6P levels increased during the first decline in adenosine triphosphate but remained relatively steady thereafter. Whereas many of the myocardial cells fixed after 5 min contracted on contact with glutaraldehyde, all cells examined after 15 to 40 min were relaxed. A progressive increase in the proportion of contracted cells was observed during the rapid increase in myocardial rigidity. During this late contraction the cells showed morphological evidence of irreversible injury. These findings suggest that ischaemic myocytes contract just before actin and myosin become strongly linked to maintain the state of rigor mortis.

The effects of ultrasound on the mechanical properties of rat cardiac muscle

The mechanical properties of cardiac muscle during ultrasonic irradiation have been studied in vitro. Left anterior papillary muscle from normal rats was suspended in buffered lactated Ringers solution equilibrated with 95% O 2, and 5% CO 2 and maintained at 20°C. The muscles were stimulated to contract isometrically three times per minute at the length which produced maximum tension. Each muscle was irradiated with 1 MHz ultrasound at an average power of 2.4 Wcm −2 for a period of 10 min with a 10 min recovery period. Irradiation caused an average increase in temperature of the muscle of 1.7 ± 0.2°C (mean ± SEM). Irradiation caused the resting tension (1.46 ± 0.13g) to decrease by 17.8 ± 4.7% and the developed tension (3.33 ± 0.61 g) to decrease by 4.1 ± 0.9%. Since changes in contractile properties have been reported with temperature the bath temperature was raised and changes in contraction observed. When compensated for effects of temperature, the changes in resting tension became − 13.3 ± 4.1% while the change in developed tension became + 1.6 ± 2.3%. The change in resting tension is highly significant ( p < 0.05 paired t-test) while the change in developed tension is not. Thus 1 MHz ultrasound at an intensity of 2.4 Wcm −2 appears to affect resting tenstion of cardiac muscle without affecting the active tension. Since changes in cardiac mechanics of this type have not been described previously the effects of ultrasound appears to be unique.

Intramural coronary arteriosclerosis of normal and dwarfed swine.

Dwarfing of swine maintained in large groups with relatively little space per animal may be attributed to psychosocial factors. Intramural coronary arteriosclerosis developed at approximately the same rate in dwarfed and normally developing animals. Lesions in arteries of the left posterior papillary muscle were more advanced than in the left anterior papillary muscle of the same animal, irrespective of its growth rate, and often were more advanced than in swine twice as old.

Spontaneous rupture of a papillary muscle of the heart: Report of case

This is the report of a case of very marked atherosclerosis of the coronary arteries, thrombosis of the anterior descending branch of the left coronary, infarction of the myocardium in the anterior wall of the left ventricle, spontaneous rupture of the left anterior papillary muscle, acute pulmonary edema, and sudden death.