Disease relevance of Bundle of His

• Proximal location of the A-V heart block was suggested by the fact that atropine caused acceleration of the ventricular rate and by the presence of a His bundle potential preceding the QRS complexes [1].
• The effects of intravenous procainamide infusion of 10--14 mg/kg body weight (i.e., 750 mg) of procainamide (PA) on reentry within the His-Purkinje system (HPS) were studied in 13 patients using His bundle electrograms and ventricular extrastimulus method [2].
• Lidocaine and His bundle extrasystoles. His bundle discharge conducted with functional right of left bundle-branch block, or blocked entirely (concealed) [3].
• BACKGROUND: Progressive cardiac conduction defect is a frequent disease commonly attributed to degeneration and fibrosis of the His bundle and its branches [4].
• No differences in the density or proportions of beta 1- and beta 2-adrenoceptors in the atrioventricular node, bundle of His, interatrial septum and interventricular septum were observed between hearts with idiopathic dilated cardiomyopathy or ischemic heart disease (P > 0.05) so further analysis did not distinguish between the two aetiologies [5].

High impact information on Bundle of His

• Using His bundle recording techniques, we examined direct and autonomically mediated conduction system effects of quinidine in five cardiac transplant recipients who have anatomically denervated hearts [6].
• By recording atrial, His, and ventricular signals with intracardiac electrodes, we show that this decrease is attributed to significantly accelerated conduction above the His bundle (atrial-His interval: 27.9 +/- 5.1 ms in Cx30.2(LacZ/LacZ) versus 37.1 +/- 4.1 ms in Cx30.2(+/+) mice), whereas HV conduction is unaltered [7].
• HNK-1 stains the developing atrioventricular conduction system, ie, the bundle branches, His bundle, right atrioventricular ring, and retroaortic ring [8].
• The diastolic slopes were recorded through a unipolar lead consisting of a terminal of an electrode catheter placed in the His bundle area paired with an indifferent terminal on the superior vena cava [9].
• Electrophysiologic studies using the His bundle electrogram (HBE) and histologic studies of serial sections of the conduction system were correlated in two groups of deceased patients [10].

Chemical compound and disease context of Bundle of His

• In normoxic hearts, N-0861 competitively and reversibly antagonized stimulus to His bundle interval prolongation induced by adenosine (1-30 microM) but not that caused by carbachol (0.09 microM), verapamil (1 microM), MgCl2 (6.5 mM) or hypothermia [11].
• However, the same dose of PD 81,723 caused a significant leftward and upward shift of the adenosine dose-response curve for inducing atrium to His bundle interval prolongation and increased the degree of atrioventricular block caused by adenosine.(ABSTRACT TRUNCATED AT 250 WORDS)[12]
• Complete heart block in dogs was induced by injecting the His bundle with formalin [13].
• Electrophysiologic effects of an acute beta-blockade induced by bisoprolol in patients with supraventricular tachycardia as assessed by His-bundle electrograms [14].
• Time to peak creatine kinase-MB activity was unrelated to either underlying cardiac disease (normal: 3.9 +/- 1.0 hours; ischemic heart disease: 3.5 +/- 0.9 hours; cardiomyopathy: 3.8 +/- 0.9 hours), or fulguration site (His bundle (n = 9): 4.2 +/- 0.9 hours, proximal coronary sinus (n = 3): 3.3 +/- 0.3 hours, ventricle (n = 9): 3.4 +/- 0.8 hours) [15].

Biological context of Bundle of His

• In 19 dogs, ventricular monophasic action potential durations (MAP), ventricular effective refractory periods (VERP) and His bundle electrograms (A-H and H-V intervals) were measured at base line and during sequential infusions of isoproterenol, dl-propranolol and dl-propranolol plus an isoproterenol infusion designed to overcome beta blockade [16].
• Therefore, in the absence of Cx40, the upregulation of Cx45 in the heart results in a normal impulse propagation in the right atrium, the AV node, and the left His bundle branch only [17].

Anatomical context of Bundle of His

• Apparent moulding of A-V node and His bundle was a universal finding in both SIDS and ED, and consisted of irregular interdigitation of A-V node and His bundle fibers with the myxoid central fibrous body (CFB) [18].
• In 11 normotensive subjects with normal atrioventricular conduction, we altered baroreceptor activity by injection of pressor and depressor drugs (phenylephrine and trinitroglycerin) and recorded mean arterial pressure (MAP, catheter measurements), R-R interval, and pre-His and post-His intervals (A-H and H-V, His bundle recording) [19].
• No labeling was detected in ventricular myocytes, including those of the His bundle and the bundle branches, which otherwise do express connexin43 (Cx43) [20].
• In six adult mongrel dogs anesthetized with pentobarbital (Nembutal), 5F leads were placed through femoral and external jugular veins and placed into the right atrium and His bundle region [21].
• In 30 patients undergoing coronary angiography the effects of Iopamidol on sinus node activity, atrioventricular and intraventricular conduction were evaluated using His Bundle recordings, and compared to the effects produced by Diatrizoate [22].

Associations of Bundle of His with chemical compounds

• The H-V interval during sinus rhythm and the S1 V1 interval during His bundle pacing at all CLs did not change after ouabain [23].
• A repeat electrophysiologic study 4 days after digoxin was discontinued revealed complete trifascicular block (distal to H) with intact conduction between the atrium and the His bundle (AH of 150 msec) [24].
• Both adenosine and ATP depressed AV conduction by lengthening the atrial to His bundle (AH) interval [25].
• During retrograde refractory period studies, the longest V1V2 interval at which a retrograde His bundle potential (H2) emerged from the V2 electrogram (relative refractory period of the His-Purkinje system) was consistently longer after amiodarone as compared with the control period (376.4 +/- 46.6 versus 318.8 +/- 33.1 ms, p less than 0.005) [26].
• In guinea pig isolated hearts, m-DITC-ADAC (5 microM) prolonged the stimulus to His bundle (SH) interval by 2.1-fold; this response could be prevented by the antagonist 8-cyclopentyltheophylline (5 microM) [27].

Gene context of Bundle of His

• We find that Tbx5 is expressed throughout the central conduction system, including the atrioventricular bundle and bundle branch conduction system [28].
• For example, Cx40 deficiency results in sinoatrial conduction impairments, a significant decrease of the conduction velocity in the atria, and a delay of the propagation of impulse in the His bundle [29].
• It is concluded that the AVN derives from the atrioventricular canal myocardium, the bundle of His from the ventricular myocardium, and the bundle branches from the ventricular trabeculations [30].
• Cx43 is not detected either in the His bundle or in the proximal parts of the bundle branches, and consequently, Cx40 is the first connexin demonstrated in this region of the rat conduction system [20].
• However, the ventricular part of the conduction system, comprising atrioventricular bundle and bundle branches, are almost devoid of SERCA2 mRNA [31].

Analytical, diagnostic and therapeutic context of Bundle of His

• Three patients with block distal to the His bundle by HBE showed a loss of electrical potential before the QRS in the surface-averaged ECG, but had a consistent HPA after the P waves [32].
• Three patients with paroxysmal supraventricular tachycardia underwent electrophysiologic studies that included His bundle recordings, incremental atrial and ventricular pacing and extrastimulation before and after intravenous infusion of 500 mg of procainamide [33].
• Forty-eight patients with predominant aortic stenosis underwent His bundle electrography (HBE) at the time of diagnostic catheterization [34].
• Left heart catheterization and His bundle registration were performed in 14 Labrador dogs anesthetized with pentobarbital [35].
• Within 1 h of perfusion, desethylamiodarone caused a more pronounced prolongation of the AV-nodal, His-bundle, and intraventricular conduction intervals than did amiodarone [36].

References