Abstract 25: Polyphenolic - Ellagic Acid Suppresses Mitophagy- Induced Necrotic Cell Death During Doxorubicin Cardiotoxicity

Reactive oxygen species (ROS) play a major role in cardiac dysfunction during myocardial ischemia. ROS production has been linked to oxidative stress injury and mitochondrial perturbations including permeability transition pore opening (mPTP), loss of mitochondrial membrane potential ([[Unable to Display Character: ∆]]Ψm) and necrotic cell death. Previously we identified the inducible Bcl-2 protein, Bnip3 as critical regulator of mitochondrial function and cell death of ventricular myocytes. Polyphenolic compounds including ellagic acid from pomegranate, have strong anti-oxidant properties. The effects of ellagic acid on oxidative stress injury in the heart has not been explored. In this report, we provide new compelling evidence that ellagic acid suppressed mitochondrial ROS production, loss of [[Unable to Display Character: ∆]]Ψm and necrotic cell death of cardiac myocytes induced by doxorubicin (DOX) or hypoxia. We further show mechanistically that the cytoprotective effects of ellagic acid were related to the transcriptional repression of Bnip3. In contrast to vehicle treated cells, cells treated with DOX or hypoxia displayed a marked increase in Bnip3 expression and mitochondrial association, concordant with increased ROS, mPTP, and loss of [[Unable to Display Character: ∆]]Ψm. Consistent with these mitochondrial defects there was a marked increase in mitophagy as confirmed by the dual emission Mitokeima probe that detects autophagic degradation by labelling mitochondria containing autophagosomes fused with lysosome. Mitophagy was accompanied by a marked increase in LDH release, loss of nuclear HMGB1 immunostaining and cell death. Interestingly, cells treated with ellagic acid were resistant to mitochondrial and the cytotoxic effects of DOX displaying reduced ROS production, mitophagy and were indistinguishable from vehicle treated control cells with respect to cell viability. Notably, Dox-induced Bnip3 expression was dramatically reduced in cells treated with ellagic acid. Hence, the findings of the present study demonstrate that ellagic acid suppresses mitochondrial perturbations and cell death of cardiac myocytes by mechanism that links to the repression of mitochondrial Bnip3.

Mitochondrial dynamics: Orchestrating the journey to advanced age

Aging is a degenerative process that unfortunately is an inevitable part of life and risk factor for cardiovascular disease including heart failure. Among the several theories purported to explain the effects of age on cardiac dysfunction, the mitochondrion has emerged a central regulator of this process. Hence, it is not surprising that abnormalities in mitochondrial quality control including biogenesis and turnover have such detrimental effects on cardiac function. In fact mitochondria serve as a conduit for biological signals for apoptosis, necrosis and autophagy respectively. The removal of damaged mitochondria by autophagy/mitophagy is essential for mitochondrial quality control and cardiac homeostasis. Defects in mitochondrial dynamism fission/fusion events have been linked to cardiac senescence and heart failure. In this review we discuss the impact of aging on mitochondrial dynamics and senescence on cardiovascular health. This article is part of a Special Issue entitled: CV Aging.

Regulation of mitochondrial dynamics and cell fate

Though the mitochondrion was initially identified as a key organelle essentially required for energy production and oxidative metabolism, there is considerable evidence that mitochondria are intimately involved in regulating vital cellular processes, such as programmed cell death, proliferation and autophagy. Discovery of mitochondrial "shaping proteins" (Dynamin-related protein (Drp), mitofusins (Mfn) etc.) has revealed that mitochondria are highly dynamic organelles continually changing morphology by fission and fusion processes. Several human pathologies, including cancer, Parkinson's disease, Alzheimer's disease and cardiovascular diseases, have been linked to abnormalities in proteins that govern mitochondrial fission or fusion respectively. Notably, in the context of the heart, defects in mitochondrial dynamics resulting in too many fused and/or fragmented mitochondria have been associated with impaired cardiac development, autophagy, and contractile dysfunction. Understanding the mechanisms that govern mitochondrial fission/fusion is paramount in developing new treatment strategies for human diseases in which defects in fission or fusion is the primary underlying defect. Here, we provide a comprehensive overview of the cellular targets and molecular signaling pathways that govern mitochondrial dynamics under normal and disease conditions.  (Circ J 2014; 78: 803-810).

Management of temporomandibular joint ankylosis type III: lateral arthroplasty as a treatment of choice

Many surgical techniques for the management of temporomandibular joint (TMJ) ankylosis have been described in the literature. The purpose of this study was to report our experience using a lateral arthroplasty technique in the management of type III ankylosis. The records of 15 patients treated for TMJ ankylosis at our institution between 2007 and 2011 were reviewed. Pre- and postoperative information collected included age, gender, aetiology, ankylosis type/classification, existing facial asymmetry, maximum pre- and postoperative mouth opening, complications, and recurrence of ankylosis. The mean maximum inter-incisal opening in the preoperative period was 12.9 mm and in the postoperative period was 36.2mm. No major complication was observed in any patient. No recurrence was noted in any patient. Our working hypothesis was that for patients with ankylosis type III, the medially displaced condyle and disc can fulfil their role in mandibular function and growth after extirpation of the ankylozed mass. Although they are located in an awkward medial position, they should function exactly as they would after a properly treated, displaced condylar fracture.

Abstract 268: Epigenetic Regulation Of Canonical Tnfa Pathway By Hdac1 Determines Survival Of Cardiac Myocytes

Gene transcription is regulated by post-translation modifications. Histone deacetylases (HDACs) remove acetyl-groups from histone and non-histone factors inhibiting transcription. Pro-inflammatory cytokines such as TNFα activate the canonical Nuclear Factor -κB (NF-κB) pathway. Earlier we established a cytoprotective role for NF-κB in the heart. Though a causal relationship for HDAC1 and NF-κB has been established, the impact of HDAC1 on TNFα signaling is unknown. Herein, we demonstrate HDAC1 provides a molecular switch for determining cell survival in the TNFα pathway. In contrast to vehicle treated control cells, TNFα treated cells displayed a marked increase in NF-κB gene transcription. Notably, cells treated with TNFα were indistinguishable from vehicle controls cells with respect to viability. Interestingly, HDAC activity was reduced in cells treated with TNFα. Conversely, in the presence of HDAC1, NF-κB gene transcription by TNFα was repressed, resulting in mitochondrial perturbations and widespread cell death. Heterologous fusion proteins comprised of yeast Gal4 DNA binding domain fused in frame to the NF-κB p65 transactivation domain were preferentially repressed by HDAC1. Moreover, transcription mediated by Gal4VP16 protein from herpes virus was unaffected by HDAC1 in cardiac myocytes. Mutations that abrogate known catalytic activities of HDAC1, small interference RNA or pharmacological inhibition of HDAC1, restored NF-κB signaling and suppressed cell death induced by TNFα. These data provide the first evidence for an obligate link between HDAC1 and canonical TNFα pathway for cell survival of cardiac myocytes.

p53 mediates autophagy and cell death by a mechanism contingent on Bnip3

Myocardial ischemia and angiotensin II activate the tumor suppressor p53 protein, which promotes cell death. Previously, we showed that the Bcl-2 death gene Bnip3 is highly induced during ischemia, where it triggers mitochondrial perturbations resulting in autophagy and cell death. However, whether p53 regulates Bnip3 and autophagy is unknown. Herein, we provide new compelling evidence for a novel signaling axis that commonly links p53 and Bnip3 for autophagy and cell death. p53 overexpression increased endogenous Bnip3 mRNA and protein levels resulting in mitochondrial defects leading to loss of mitochondrial ΔΨ(m). This was accompanied by an increase in autophagic flux and cell death. Notably, genetic loss of function studies, such as Atg7 knock-down or pharmacological inhibition of autophagy with 3-methyl adenine, suppressed cell death induced by p53--indicating that p53 induces maladaptive autophagy. Our previous work demonstrated that Bnip3 induces mitochondrial defects and autophagic cell death. Conversely, loss of function of Bnip3 in cardiac myocytes or Bnip3(-/-) mouse embryonic fibroblasts prevented mitochondrial targeting of p53, autophagy, and cell death. To our knowledge, these data provide the first evidence for the dual regulation of autophagy and cell death of cardiac myocytes by p53 that is mutually dependent on and obligatorily linked to Bnip3 gene activation. Hence, our findings may explain more fundamentally, how, autophagy and cell death are dually regulated during cardiac stress conditions where p53 is activated.

Striking a balance: autophagy, apoptosis, and necrosis in a normal and failing heart

Despite the progress that has been made over the past two decades in cardiovascular research, heart failure remains a major cause of morbidity and mortality worldwide. Insight into the cellular and molecular mechanisms that underlie the heart failure in individuals with ischemic heart disease have identified defects in cellular processes that govern autophagy, apoptosis and necrosis as a prevailing underlying cause. Indeed, programmed cell death of cardiac cells by apoptosis or necrosis is believed to involve the intrinsic mitochondrial pathway and/or extrinsic death receptor pathway by certain Bcl-2 family members as well as components of the TNFα signaling pathway. In this review, we discuss recent advances in the molecular signaling factors that govern cardiac cell fate under normal and disease conditions.

Epigenetic regulation of canonical TNFα pathway by HDAC1 determines survival of cardiac myocytes

Gene transcription is regulated by post-translation modifications. Histone deacetylases (HDACs) remove acetyl groups from histone and non-histone factors inhibiting transcription. Proinflammatory cytokines such as TNFα activate the canonical nuclear factor-κB (NF-κB) pathway. Earlier we established a cytoprotective role for NF-κB in the heart. Though a causal relationship for HDAC1 and NF-κB has been established, the impact of HDAC1 on TNFα signaling is unknown. Herein, we demonstrate that HDAC1 provides a molecular switch for determining cell survival in the TNFα pathway. In contrast to vehicle-treated control cells, TNFα-treated cells displayed a marked increase in NF-κB gene transcription. Notably, cells treated with TNFα were indistinguishable from vehicle controls cells with respect to viability. Interestingly, HDAC activity was reduced in cells treated with TNFα. Conversely, in the presence of HDAC1, NF-κB gene transcription by TNFα was repressed, resulting in mitochondrial perturbations and widespread cell death. Heterologous fusion proteins comprised of yeast Gal4 DNA binding domain fused in frame to the NF-κB p65 transactivation domain were preferentially repressed by HDAC1. Moreover, transcription mediated by Gal4VP16 protein from herpes virus was unaffected by HDAC1 in cardiac myocytes. Mutations that abrogate known catalytic activities of HDAC1, small interference RNA, or pharmacological inhibition of HDAC1 restored NF-κB signaling and suppressed cell death induced by TNFα. These data provide the first evidence for an obligate link between HDAC1 and canonical TNFα pathway for cell survival of cardiac myocytes.

Bidirectional regulation of nuclear factor-κB and mammalian target of rapamycin signaling functionally links Bnip3 gene repression and cell survival of ventricular myocytes

BACKGROUND

Tumor necrosis factor-α and other proinflammatory cytokines activate the canonical nuclear factor (NF)-κB pathway through the kinase IKKβ. Previously, we established that IKKβ is also critical for Akt-mediated NF-κB activation in ventricular myocytes. Akt activates the kinase mammalian target of rapamycin (mTOR), which mediates important processes such as cardiac hypertrophy. However, whether mTOR regulates cardiac myocyte cell survival is unknown.

METHODS AND RESULTS

Herein, we demonstrate bidirectional regulation between NF-κB signaling and mTOR, the balance which determines ventricular myocyte survival. Overexpression of IKKβ resulted in mTOR activation and conversely overexpression of mTOR lead to NF-κB activation. Loss of function approaches demonstrated that endogenous levels of IKKβ and mTOR also signal through this pathway. NF-κB activation by mTOR was mediated by phosphorylation of the NF-κB p65 subunit increasing p65 nuclear translocation and activation of gene transcription. This circuit was also important for NF-κB activation by the canonical tumor necrosis factor-α pathway. Our previous work has shown that NF-κB signaling suppresses transcription of the death gene Bnip3 resulting in ventricular myocyte survival. Inhibition of mTOR with rapamycin decreased NF-κB activation resulting in increased Bnip3 expression and cell death. Conversely, mTOR overexpression suppressed Bnip3 levels and cell death of ventricular myocytes in response to hypoxia.

CONCLUSIONS

To our knowledge, these data provide the first evidence for a bidirectional link between NF-κB signaling and mTOR that is critical in the regulation of Bnip3 expression and cardiac myocyte death. Hence, modulation of this axis may be cardioprotective during ischemia.

Abstract 224: Crosstalk Between Mitochondrial and ER Death Pathways in the Heart

Alternative gene splicing provides a versatile mechanism by which cells generate proteins with different or even antagonistic properties. Previously we determined the hypoxia-inducible protein Bnip3 is integral component of the mitochondrial death pathway that can signal apoptosis and autophagy but the precise mechanisms that differentially regulates these divergent processes remains cryptic. Herein, we provide novel evidence that inclusion or skipping of exon3 of Bnip3 mRNA by alternative splicing generates proteins with distinct and opposing actions on autophagy and cell survival. Metabolic stress imposed by hypoxia or nutrient deprivation resulted in the synthesis of two Bnip3 mRNA isoforms in post-natal ventricular myocytes in vitro and in vivo. Notably, one Bnip3 mRNA comprised of exons 1 through exon 6 encoded a protein of 26kDa, while a second mRNA generated by the fusion of exon2 and exon4 encoded a truncated Bnip3 protein of 8.2kDa. Sequence analysis revealed the truncated isoform encodes a conserved C-terminus domain that exclusively targets Bnip3 to the endoplasmic reticulum and not mitochondrion. While the 26kDa Bnip3 induced mitochondrial perturbations and autophagy, the spliced variant suppressed Bnip3- induced mitochondrial defects and autophagy. Furthermore, genetic knock-down or mutations within the C-terminus of the spliced variant defective for ER targeting sensitized cardiac myocytes to mitochondrial ROS production and death. To our knowledge our data provide the first direct evidence for a novel survival mechanism whereby the metabolic status of the cell programs autophagy or apoptosis by preferentially targeting Bnip3 isoforms to mitochondria or ER during metabolic stress.

A novel hypoxia-inducible spliced variant of mitochondrial death gene Bnip3 promotes survival of ventricular myocytes

RATIONALE

Alternative splicing provides a versatile mechanism by which cells generate proteins with different or even antagonistic properties. Previously, we established hypoxia-inducible death factor Bnip3 as a critical component of the intrinsic death pathway.

OBJECTIVE

To investigate alternative splicing of Bnip3 pre-mRNA in postnatal ventricular myocytes during hypoxia.

METHODS AND RESULTS

We identify a novel previously unrecognized spliced variant of Bnip3 (Bnip3Δex3) generated by alternative splicing of exon3 exclusively in cardiac myocytes subjected to hypoxia. Sequencing of Bnip3Δex3 revealed a frame shift mutation that terminated transcription up-stream of exon5 and exon6 ablating translation of the BH3-like domain and critical carboxyl-terminal transmembrane domain crucial for mitochondrial localization and cell death. Notably, although the 26-kDa Bnip3 protein (Bnip3FL) encoded by full-length mRNA was localized to mitochondria and provoked cell death, the 8.2-kDa Bnip3Δex3 protein encoded by the truncated spliced mRNA was defective for mitochondrial targeting but interacted with Bnip3FL resulting in less association of Bnip3FL with mitochondria and diminished apoptotic and necrotic cell death. Forced expression of Bnip3FL in cardiac myocytes or Bnip3(-/-) mouse embryonic fibroblasts triggered widespread cell death that was inhibited by coexpression of Bnip3Δex3. Conversely, RNA interference targeted against sequences encompassing the unique exon2-exon4 junction of the Bnip3Δex3 sensitized cardiac myocytes to mitochondrial perturbations and cell death induced by Bnip3FL.

CONCLUSIONS

Given the otherwise lethal consequences of deregulated Bnip3FL expression in postmitotic cells, our findings reveal a novel intrinsic defense mechanism that opposes the mitochondrial defects and cell death of ventricular myocytes that is obligatorily linked and mutually dependent on alternative splicing of Bnip3FL during hypoxia or ischemic stress.

Hibernating myocardium: pathophysiology, diagnosis, and treatment

Comprehensive management of patients with chronic ischemic disease is a critically important component of clinical practice. Cardiac myocytes have the potential to adapt to limited flow conditions by adjusting contractile function, reducing metabolism, conserving resources, and preserving myocardial integrity to cope with an oxygen and (or) nutrition shortage. A prime metabolic feature of cardiac myocytes affected by chronic ischemia is the return to a fetal gene pattern with predominance of carbohydrates as the substrate for energy. Structural adaptation with multiple intracellular changes is part of the remodeling process in hibernating myocardium. Transmural heterogeneity, which defines the pattern of injury in ventricular cardiomyocytes and the response to chronic ischemia, is a multifactorial process originating from functional, metabolic, and flow differences in subendocardial and subepicardial regions. Autophagy is typically activated in hibernating myocardium and has been identified as a prosurvival mechanism. Chronic ischemia is associated with changes in the number, size, and distribution of gap junctions and may give rise to conduction disturbances and arrhythmogenesis. Differentiation between viable and nonviable myocardium by assessing sensitivity of inotropic reserve is a crucial diagnostic tool that is correlated with the prognosis and outcome for improved contractility after restoration of blood perfusion in afflicted myocardium.Reliable and accurate diagnosis of ischemic, scar, and viable tissues is critical for recover strategies. Although early surgical reinstitution of blood flow is most effective in restoring physiologic function of the hibernating myocardium, several new approaches offer promising alternatives. Among others, vascular endothelial growth factor and fibroblast growth factor-2 (FGF-2), especially its lo-FGF-2 isoform, have been shown to be effective in rapid neovascularization. Substances such as statins, resveratrol, some hormones, and omega-3 fatty acids can improve recovery effect in chronically underperfused hearts. For patients with drug-refractory ischemia, intramyocardial transplantation of stem cells into predefined areas of the heart can enhance vascularization and have beneficial effects on cardiac function. This review of ischemic injury, its heterogeneity, accurate diagnosis, and newer methods of treatment, shows there is much information and tremendous hope for better management of patients with coronary heart disease.

An evaluation of the referral transport system of Patna, Bihar

OBJECTIVES

The key objective of the study was to evaluate the coverage and functioning of the referral transport system under NRHM in block PHCs of district Patna in Bihar.

METHODS

A cross-sectional descriptive study was conducted during October-November, 2008 in 16 block PHCs in Patna. In-depth interviews were conducted at 811 households where there was an occasion to transfer a patient to a hospital in the previous two months time. Medical officer in-charge and civil surgeon of the district were also interviewed. Besides, focus group discussions were conducted with the community members and leaders regarding the functioning of referral transport.

RESULTS

Availability of the referral transport services was irregular mainly due to deputation of the vehicles for flood relief activities or other purposes. 93 (11.5%) of respondents used the PHC transport facilities, of which 52.7% got it instantaneously. 'Dial an ambulance 102' services were mainly used by urban clients. The system was following an arbitrary cost structure. 84.2% of the clients belonging to below poverty line had to pay for the service and are afraid of availing the services.

CONCLUSION

Inadequate number of ambulances in PHCs, unequipped ambulances, lack of life saving equipments, 24 hours duty by single driver, arbitrary cost frame work and urban preference for services were some of the factors leading to unpopularity of the scheme.

Unusual nerve supply of biceps from ulnar nerve and median nerve and a third head of biceps

Variations in branching pattern of the brachial plexus are common and have been reported by several investigators. Of the four main nerves traversing the arm, namely median, ulnar, radial and musculocutaneous, the ulnar and median nerve do not give any branches to muscles of the arm. Ulnar nerve after taking origin from medial cord of brachial plexus runs distally through axilla on medial side of axillary artery till middle of arm, where it pierces the medial intermuscular septum and enters the posterior compartment of arm. Ulnar nerve enters forearm between two heads of flexor carpi ulnaris from where it continues further. It supplies flexor carpi ulnaris , flexor digitorum profundus and several intrinsic muscles of hand . We recently observed dual supply of biceps muscle from ulnar and median nerves in arm. Musculocutaneous nerve was absent. Although communications between nerves in arm is rare, the communication between median nerve and musculocutaneous nerve were described from the 19th century which could explain innervation of biceps from median nerve. But no accurate description of ulnar nerve supplying biceps could be found in literature. Knowledge of anatomical variation of these nerves at level of upper arm is essential in light of the frequency with which surgery is performed to transfer nerve fascicles from ulnar nerve to biceps in case of brachial plexus injuries. We also observed third head of biceps, our aim is to describe the exact topography of this variation and to discuss its morphological.

Absence of musculocutaneous nerve and accessory head of biceps brachii: a case report

During dissection of a 55-year-old female cadaver, we observed that three nerve roots contributed to the formation of Median nerve in her right upper limb. Along with this variation, absence of Musculocutaneous nerve was noticed. The muscles of front of arm i.e. Biceps Brachii, Brachialis and Coracobrachialis received their nerve supply from Median nerve. The Lateral cutaneous nerve of forearm was derived from Median nerve. Also an accessory head of Biceps Brachii muscle was present in the right arm of the same cadaver. It is extremely important to be aware of these variations while planning a surgery in the region of axilla or arm as these nerves are more liable to be injured during operations.

An experimental design for induction of non-specific aortoarteritis

BACKGROUND

An attempt was made to induce aortoarteritis in mice by using various antigens.

METHODS AND RESULTS

The Swiss mice were immunized with eight different antigens and were grouped A to G. Group H served as control. The mice were then bled at 1st, 2nd, 4th, 6th and 8th month interval post-immunization for estimating antibody titer. Then the mice were sacrificed and the heart, aorta and kidney were taken out and processed for hematoxylin-eosin staining. There was gradual increase in the antibody titer from 1st month till 4th month within all the experimental groups (A-G), when compared with control group H. The titer started falling sharply from 6th month post-immunization. However, the control group H did not show much variation. When each individual group was compared separately with control group H, the significant statistical value was obtained. Histopathological examination revealed mild inflammation (+) in kidney by 2nd month, moderate inflammation (++) by 6th month, extensive inflammation (+++) by 8th month and alteration in the normal parenchyma of kidney by 8th month.

CONCLUSIONS

The histopathological changes brought out through antigens were more pronounced by 8th month following injection of tunica media, tunica adventitia, tunica intima and aorta collagen as compared to that of standard collagen and mouse aorta injections.

Enzyme-linked immunosorbent assay and immunoblot study in Takayasu's arteritis patients

Takayasu's arteritis or non-specific aortoarteritis is an inflammatory and stenotic disease of the aorta of questionable aetiology. Immunopathogenic mechanism, the precise nature of which is uncertain, is often suspected to be one of the basic causes of this disease. The present study was designed to estimate the antiaorta antibody titre in Takayasu's arteritis patients and to further locate the antigen in the vessel wall. Thirty clinically and angiographically proven cases of Takayasu's arteritis patients with appropriate controls were studied. Antiaorta antibody titres were estimated using Enzyme-Linked Immunosorbent Assay method. The controls included patients of vascular diseases other than Takayasu's arteritis, autoimmune diseases like rheumatoid arthritis and systemic lupus erythematosis and normal healthy individuals. Absorbance value at 492 nm at a dilution of 1:500 of the patients' sera was expressed as the antiaorta, antibody titre. There was significant difference (p < 0.005) between the mean value of the antibody titre in patients (0.471 +/- 0.073) and patients of other vascular diseases (0.209 +/- .056); autoimmune diseases (0.143 +/- .024); and, controls (0.108 +/- 0.012). Collagenase treatment of the aorta resulted in the fall of the antibody titre of aortitis patients (0.162 +/- 0.036) suggesting that the collagen might be one of the components responsible for autoantigenecity of aorta resulting in aortitis. The aortic extract was further subjected to 10 percent sodium dodecyle sulphate-polyacrylamide gel electrophoresis and immunoblot was done with Takayasu's arteritis patients' sera as well as controls' sera. The sera in 80 percent of Takayasu's arteritis patients immunoprecipitated a protein of molecular weight 45,000 (45 kilodalton) whereas only 15 percent patients of autoimmune disease group showed precipitation band though of lower molecular weight. Normal human sera gave no immunoprecipitation band. The precise nature of the antigen still needs to be identified.

An enzyme linked immunosorbent assay for detection of anti-aorta antibodies in Takayasu arteritis patients

Thirty cases of clinically and angiographically proven non-specific aortoarteritis with appropriate controls were studied. Antiaorta antibody titres were estimated using enzyme linked immunosorbent assay (ELISA) method. The controls included patients of vascular diseases other than non-specific aortoarteritis, autoimmune diseases (rheumatoid arthritis and systemic lupus erythematosis), and normal healthy individuals. An absorbance value at 492 nm at a dilution of 1:500 of patients' sera was expressed as the antiaorta antibody titre. There was a significant difference (P < 0.005) between the mean value of the antibody titre of non-specific aortoarteritis patients (0.471 +/- 0.073) and patients of other vascular diseases (0.209 +/- 0.056), autoimmune disease patients (0.143 +/- 0.024) and controls (0.108 +/- 0.012). Collagenase treatment of the aorta resulted in the fall of the antibody titre of aortitis patients (0.162 +/- 0.036) suggesting that the collagen might be one of the components responsible for autoantigenecity of the aorta resulting in aortitis. The precise nature of the antigen needs to be identified.

Serial electrophysiologic studies in patients with chronic bundle branch block

Serial His bundle recordings were obtained during 1:1 atrioventricular (AV) conduction in 90 patients with chronic bundle branch block over a mean interval of 30 months. Atrioventricular conduction time (AH) increased greater than or equal to 10 msec in 25 (28%) and infranodal conduction time (HV) increased greater than or equal to 8 msec in 29 (32%), but only 10 patients had parallel increases in AH and HV intervals. Increases in conduction times were independent of age, time interval between studies, cause of heart disease or initial AH or HV intervals. Women were significantly more likely than men to show an increased HV interval and spontaneous trifascicular block. Spontaneous progression to second- or third-degree AV block occurred at the AV node in seven patients and below the node in 12 patients. The initial AH interval was prolonged in five of seven patients (71%) with AV nodal block and had increased further in only two at restudy. The initial HV interval was abnormal in eight of 12 patients (67%) who progressed to infranodal block and was prolonged further in eight at restudy. We conclude that in patients with chronic bundle branch block, (1) approximately 33% show progressive AV conduction system disease and AV nodal and infranodal disease progress independently; (2) progression of infranodal disease is more common in women; (3) AV nodal disease progress independently; (2) progression of infranodal disease is more common in women; (3) AV nodal disease is a common cause of AV block and can occur without further prolongation of the AH interval once a critical level of disease is attained, whereas infranodal block is usually accompanied by progressive lengthening of the HV interval; and (4) progression of AV conduction disease is not readily predictable from clinical and electrophysiologic variables.

Chronic longterm electrophysiologic study of paroxysmal ventricular tachycardia

Nine patients with recurrent paroxysmal ventricular tachycardia underwent chronic electrophysiologic studies to delineate effective drug therapy for prevention of recurrence of this arrhythmia. The frequency of attacks of ventricular tachycardia necessitating hospitalization ranged from 2 to 12 (mean 5 +/- 4) attacks per year. Pacing induction of ventricular tachycardia was performed prior to and following intravenous or oral administration of procainamide (eight patients), disopyramide phosphate (nine patients), aprindine (five patients) and propranolol (four patients). Successful drug response (prevention of ventricular tachycardia induction or induction of nonsustained episodes of tachycardia) was noted in six of nine patients (66 percent). Lack of drug effect on the ability to sustain ventricular tachycardia was noted in three patients (34 percent). In addition, a deleterious drug response, manifested by potentiation of ventricular flutter or fibrillation, was observed in two of the three patients who failed to respond to drugs. Chronic drug therapy based on successful response in six patients resulted in cure of ventricular tachycardia in five of six patients (83 percent), one patient having one attack necessitating hospitalization. Of the three patients who demonstrated lack of drug effect during chronic electrophysiologic studies, one died suddenly and two had recurrent episodes of ventricular tachycardia while receiving a drug that did not prevent induction of ventricular tachycardia.

Paroxysmal supraventricular tachycardia induction in patients with Wolff-Parkinson-White syndrome

In 54 patients with pre-excitation, 30 (56%) had inducible A-V re-entrant paroxysmal tachycardia. Of these 30, 20 had spontaneous paroxysmal tachycardia (four also had atrial fibrillation), four had spontaneous paroxysmal atrial fibrillation, five had a history of palpitation without arrhythmia, and one was asymptomatic. In 24 patients (44%), paroxysmal tachycardia was not inducible. Of these 24, none had documented paroxysmal tachycardia, four had atrial fibrillation, none had palpitation without arrhythmia, and 11 were asymptomatic. The incidence of documented paroxysmal tachycardia was higher in the patients with inducible tachycardia (P less than 0.001). Tachycardia induction was noted in 20 of 20 patients with spontaneous paroxysmal tachycardia, eight of 12 patients with paroxysmal atrial fibrillation, five of 14 patients with palpitation and no arrhythmia, and one of 12 asymptomatic patients. The frequency of ability to induce paroxysmal tachycardia was significantly higher in both the patients with documented spontaneous paroxysmal tachycardia and the patients with paroxysmal atrial fibrillation than in the asymptomatic group (P less than 0.01).

Clinical, electrocardiographic and electrophysiologic observations in patients with paroxysmal supraventricular tachycardia

Seventy-nine patients without ventricular preexcitation but with documented paroxysmal supraventricular tachycardia were analyzed. Electrophysiologic studies suggested atrioventricular (A-V) nodal reentrance in 50 patients, reentrance utilizing a concealed extranodal pathway in 9, sinus or atrial reentrance in 7 and ectopic automatic tachycardia in 3. A definite mechanism of tachycardia could not be defined in 10 patients (including 7 whose tachycardia was not inducible). The three largest groups with inducible tachycardias were compared in regard to age, presence of organic heart disease, rate of tachycardia, functional bundle branch block during tachycardia and relation of the P wave and QRS complex during tachycardia. A-V nodal reentrance was characterized by a narrow QRS complex and a P wave occurring simultaneously with the QRS complex during tachycardia. Reentrance utilizing a concealed extranodal pathway was characterized by young age, absence of organic heart disease, fast heart rate, presence of bundle branch block during tachycardia and a P wave following the QRS complex during tachycardia. Sinoatrial reentrance was characterized by frequent organic heart disease, a narrow QRS complex and a P wave in front of the QRS complex during tachycardia. In conclusion, a mechanism of paroxysmal supraventricular tachycardia could be defined in most patients. Observations of clinical and electrocardiographic features in these patients should allow prediction of the mechanism of the tachycardia.

The determinants of atrioventricular nodal re-entrance with premature atrial stimulation in patients with dual A-V nodal pathways

In patients with dual atrioventricular (A-V) nodal pathways, atrial extrastimulus testing induces either no echoes, single atrial echoes (Ae), or repetitive re-entrance (repetitive atrial and ventricular beating). We examined the fast and slow pathways properties in 38 patients with dual pathways in order to delineate the determinants of re-entrance. Seventeen patients had no Ae. Of these, six had no V-A conduction and 11, intact V-A conduction. The mean paced ventricular cycle length producing retrograde V-A block (VABCL) in this group (a measure of retrograde fast pathway refractoriness) was 552 +/- 32 msec (mean +/- SEM; 10 pts). In contrast, all 21 patients with Ae had intact V-A conduction with mean VABCL of 382 +/- 21 msec (14 pts) (P less than 0.05). Repetitive re-entrance occurred only when Ae conducted to the ventricles. Seven patients had only single Ae. The mean paced atrial cycle length producing Wenckebach periodicity (CLAWP) in this group (a measure of antegrade slow pathway refractoriness) was 490 +/- 31 msec (5 pts). Fourteen patients had repetitive re-entrance. The mean CLAWP in this group was 399 +/- 18 msec (8 pts) (P less than 0.05). In conclusion, our results suggest that in patients with dual pathway, the occurrence of single or repetitive re-entry is dependent upon measurable slow and fast pathway properties.

An unusual variety of atrioventricular nodal re-entry due to retrograde dual atrioventricular nodal pathways

Three patients with paroxysmal supraventricular tachycardia (PSVT) had discontinuous ventriculo-artrial conduction curves (V1-V2, A1-A2), suggesting dual A-V nodal pathways. Ventricular echoes occurred simultaneously with sudden increase of V-A interval. These echoes were characterized by retrograde P waves occurring in front of QRS, suggesting utilization of a slow pathway for retrograde conduction and a fast pathway for antegrade conduction. In case one, atropine improved retrograde slow pathway and antegrade fast pathway conduction and made A-V nodal re-entry sustained, resulting in PSVT (with retrograde P in front of the QRS). In cases 2 and 3, atropine markedly shortened retrograde fast pathway refractory period and slightly improved antegrade slow pathway conduction. The discontinuous V1-V2, A1-A2 curves and echoes were no longer demonstrable. However, with improvement of retrograde fast pathway and antegrade slow pathway conduction, A-V nodal re-entrant echoes and PSVT were observed, utilizing the slow pathway for antegrade conduction and the fast pathway for retrograde conduction (P simultaneous with QRS).

Effects of cycle length on atrial vulnerability

The effect of cycle length on atrial vulnerability was studied in 14 patients manifesting reproducible repetitive atrial firing during atrial extra-stimulus (A2) testing. Repetitive atrial firing was defined as the occurrence of two or more premature atrial responses with return cycle (A2-A3) of 250 msec or less and subsequent mean cycle length of 300 msec or less, following A2. The zone of repetitive atrial firing could be defined in terms of its longest and shortest A1-A2 coupling intervals. Each patient was tested at a long cycle length (CL1) (mean 884 msec) and a short cycle length (CL2) (mean 557 msec). CL1 was sinus rhythm and CL2, an atrial paced rhythm. Repetitive atrial firing occurred in two patients at CL1 and in all patients at CL2. Of the former two patients (group 2), the zone of repetitive atrial firing was markedly widened in one at CL2 due to a shortening of atrial functional refractory period (FRP) at CL2. In the other, zone of repetitive atrial firing could not be totally defined due to induction of sustained atrial flutter preventing definition of atrial FRP. The occurrence of repetitive atrial firing at only CL2 in 12 patients (group 1) reflected: 1) a shortening of atrial FRP from 294 +/- 11 msec at CL1 to 242 +/- 10 msec at CL2 (mean +/- SEM; P less than 0.01), allowing delivery of A2 at shorter coupling intervals (9); 2) the new occurrence of repetitive atrial firing at A1-A2 coupling intervals achievable at both cycle lengths (1); or 3) both effects (2). In conclusion, decrease of cycle length potentiated atrial vulnerability. This demonstration implies that atrial pacing could potentiate occurrence of paroxysmal atrial fibrillation or flutter.

The clinical spectrum of chronic His bundle block

This report details our total experience with documented chronic His bundle block in 24 patients. Ten patients had second-degree block (eight with 2:1 block and two with type-1 block), and 14 patients had complete heart block. There were 16 women (67 percent) and eight men (33 percent) with ages ranging from 17 to 87 years. Diagnoses were as follows: hypertensive cardiovascular disease, nine patients (38 percent); arteriosclerotic heart disease, six patients (25 percent); aortic valvular disease, three patients (13 percent); primary conduction disease, two patients (8 percent); primary myocardial disease, two patients (8 percent); congenital heart block, one patient (4 percent); and traumatic heart block, one patient (4 percent). Pacing was instituted in 20 patients because of the following; congestive heart failure, seven patients; syncope, seven patients; fatigue, four patients; and recurrent dizziness, two patients. Permanent pacing was indicated within ten days of initial diagnosis in 13 patients, from 20 to 80 days in four patients, and later than 100 days in three patients. An additional two asymptomatic patients were treated with prophylactic pacing.

Pathologic correlations in three cases of bilateral bundle branch disease with unusual electrophysiologic manifestations in two cases

Examination of the conduction system in three patients with bifascicular block who had electrophysiologic studies forms the basis for this report. Patients 1 and 2 had left bundle branch block and Patient 3 right bundle branch block and left axis deviation. The H-V interval was prolonged in each case (70, 65 and 60 msec, respectively). Serial section examination of the conduction system revealed sclerodegenerative involvement of both bundle branches in all cases. In Case 1, atrial extrastimulus testing converted left to right bundle branch block; in Case 2, it delineated a sinus echo zone with repetitive sinus nodal reentrance. In the latter case serial section revealed extensive amyloid infiltration of the approaches to the sinoatrial (S-A) node and the atrial preferential pathways. In Case 3, with right bundle branch block and left axis deviation, serial section revealed greater involvement of the anterior part of the main left bundle branch than of the posterior portion as well as involvement of the second part of the right bundle branch. The study revealed excellent correlation between electrophysiologic and pathologic findings in three cases of intraventricular conduction disease and demonstrated an anatomic basis for the electrophysiologic findings resembling alternating bilateral bundle branch block. Sinus nodal reentrance may be related to disease in the approaches to the S-A node thereby causing delay in perinodal tissue allowing sinus reentrance. Finally in Case 3, the anatomic substrate for left axis deviation may lie in a greater involvement of the anterior portion than of the posterior portion of the main left bundle rather than in the corresponding portions of the periphery.

Dual atrioventricular nodal pathways. A common electrophysiological response

Evidence of dual atrioventricular nodal pathwats (a sudden jump in H1-H2 at critical A1-A2 coupling intervals) was shown in 41 out of 397 patients studied with atrial extrastimulus techniques. In 27 of these 41, dual pathways were demonstrable during sinus rhythm, or at a cycle length close to sinus rhythm (CL1). In the remaining 14, dual pathways were only demonstrated at a shorter cycle length (CL2). All patients with dual pathways at cycle length who were also tested at cycle length (11 patients) had dual pathways demonstrable at both cycle lengths. In these 11 patients both fast and slow pathway effective refractory periods increased with decrease in cycle length. Twenth-two of the patients (54%) had either an aetiological factor strongly associated with atrioventricular nodal dysfunction or one or more abnormalities suggesting depressed atrioventricular nodal function. Dvaluation of fast pathway properties suggested that this pathway was intranodal. Seventeen of the patients had previously documented paroxysmal supraventricular tachycardia (group 1). Eight patients had recurrent palpitation without documented paroxysmal supraventricular tachycardia (group 2), and 16 patients had neither palpitation nor paroxysmal supraventricular tachycardia (group 3). Echo zones were demonstrated in 15 patients (88%) in group 1, no patients in group 2, and 2 patients (13%) in group 3.

Determinants of fast- and slow-pathway conduction in patients with dual atrioventricular nodal pathways

Electrophysiological studies were performed in two patients with documented paroxysmal supraventricular tachycardia and dual atrioventricular (AV) nodal pathways as defined by the atrial extra-stimulus technique. Both patients manifested two ranges of A-H intervals (AV nodal conduction times) at critical cycle lengths, reflecting fast- and slow-pathway conduction. The occurrence of fast- and slow-pathway conduction at the same cycle length depended on a long fast-pathway effective refractory period relative to the spontaneous or driven cycle length. At critical cycle lengths with fast-pathway conduction, a shift to slow-pathway conduction could be induced by a premature atrial impulse falling within the effective refractory period of the fast pathway. Repetitive retrograde concealed conduction to the fast pathway then maintained antegrade slow-pathway conduction. Resumption of fast-pathway conduction was induced with premature atrial impulses falling within the effective refractory periods of both the fast and the slow pathways, allowing recovery of the fast pathway for antegrade conduction. Atrial echoes and AV nodal reentrant paroxysmal supraventricular tachycardia occurred when sufficient slow-pathway delay was achieved to allow recovery of the fast pathway for retrograde conduction.

New manifestations of dual A-V nodal pathways

Electrophysiological studies with extrastimulus technique demonstrated evidence of dual A-V pathways in two patients with paroxysmal supraventricular tachycardia (PSVT). In case one, the second P of paced Wenckebach sequences was followed by two conducted QRS complexes without an intervening P wave. The A-H of the first and second QRS were consistent with the fast and slow pathway conduction times. The second QRS was followed by an atrial echo and PSVT, suggesting that the first pathway was available for retrograde propagation following the second QRS. In case two, PSVT was induced with atrial extrastimulus, followed by development of A-V dissociation. The two cases suggest the following conclusions: (1) dual A-V nodal pathways may allow the occurrence of double antegrade conduction of one P; (2) the atria are not necessary for A-V nodal circus movements in "dual pathway" A-V nodal reentrant PSVT.

The effects of propranolol on induction of A-V nodal reentrant paroxysmal tachycardia

Twelve patients with paroxysmal supraventricular tachycardia (PSVT) were studied before and after administration of 0.1 mg/kg i.v. propranolol. Echo zones for inducing atrioventricular (A-V) nodal reentry were determined using His bundle recording and the atrial extrastimulus technique. After propranolol the echo zone was abolished in two patients, decreased in one, unchanged in five, increased in two. In two patients echo zones appeared only after propranolol. Nine patients had episodes of sustained PSVT prior to propranolol. Following propranolol PSVT persisted in only five. In these five patients propranolol slowed the rate of PSVT.

The data were analyzed by plotting A 1 -A 2 and H 1 -H 2 interval curves. On the basis of these curves the patients were separated into those with "dual pathways" and those with "reflection." The effects of propranolol on both conduction patterns are discussed.

In summary, the actions of propranolol in PSVT patients were variable. Potentially beneficial effects included slowing of induced PSVT, loss of the ability to sustain PSVT, and decrease or total elimination of echo zones. Potentially deleterious effects included potentiation of the echo phenomenon with either increase or development of echo zones.

Nature of the gap phenomenon in man

The atrioventricular (AV) gap phenomenon occurs when the effective refractory period of a distal site is longer than the functional refractory period of a proximal site and when closely coupled stimuli are delayed enough at the proximal site to allow distal site recovery. According to previous studies, in type 1 gap, the distal site of block is distal to the His bundle (ventricular specialized conduction system) and the proximal site of block is in the AV node. In type 2 gap, both the proximal and the distal sites of conduction block are within the ventricular specialized conduction system. Using His bundle recordings and atrial extra-stimulus techniques in man, we observed three previously undescribed types of gaps between (1) the AV node (distal) and the atrium (proximal), (2) the His bundle (distal) and the AV node (proximal), and (3) the ventricular specialized conduction system or a bundle branch (distal) and the His bundle (proximal). The delays at the His bundle in the second and third types of gaps seen in this study were demonstrated as splitting of His bundle potentials. Gaps between the AV node or the His bundle and the ventricular specialized conduction system were more easily demonstrated at long cycle lengths, but gaps between the atrium and the AV node were more easily demonstrated at short cycle lengths. Therefore, the previous subdivision of gaps into two types is an oversimplification, because gaps can occur between multiple sites in the conduction system. The gap phenomenon may be potentiated by both long and short cycle lengths; long cycle lengths increase the effective refractory period of a distal site, e.g., the His bundle and the ventricular specialized conduction system, and the short cycle lengths decrease the functional refractory period of a proximal site, e.g., the atrium and the AV node.

Pathophysiologic correlations in two cases of split His bundle potentials

This is a pathophysiological correlation in two cases showing split His bundle potentials. The first case had a history of previous complete heart block and the electrophysiological studies revealed split His potentials with intact A-V conduction. Case two had split His potentials with complete heart block. Serial sections of the conduction system in both cases revealed calcific impingement on, and degenerative changes within the bundle of His with healthy bundle of His proximal and distal to the lesion.

The effects of cycle length on cardiac refractory periods in man

The effects of pacing-induced changes in cycle length on the refractory periods of the atrium, A-V node and His-Purkinje system were studied in 24 patients using the extra stimulus technique. Refractory period determinations were made at two or more cycle lengths in all patients. Slopes relating cycle length and refractory periods were calculated using the least squares method.

Both the effective and functional refractory periods (ERP and FRP) of the atrium shortened with decreasing cycle lengths, with a mean slope of +0.155 and +0.129 respectively. A-V nodal ERP lengthened (mean slope, –0.177) while A-V nodal FRP shortened slightly (mean slope, +0.126). Bundle branch refractory periods as well as relative refractory periods of the His-Purkinje system also decreased, with mean slopes of +0.270 and +0.360, respectively. The ERP of the A-V node at any cycle length was related to the A-H at that cycle length ( r = +0.646, P < 0.001).

The responses of the human heart to changes in cycle length are generally similar to those previously described in the animal laboratory. Such information contributes to our understanding of electrocardiographic phenomena such as aberrant conduction.