Transcatheter aortic valve implantation for severe aortic stenosis in dextrocardia with situs inversus using a self-expanding aortic valve

Transcatheter aortic valve implantation (TAVI) has evolved into a standard therapy for aged patients with severe aortic valve stenosis who are not candidates for surgery. However, the reports about the safety of TAVI for patients with dextrocardia situs inversus are few. An 84-year-old man with dextrocardia situs inversus underwent a TAVI for severe aortic stenosis (AS) with an aortic valve area of 0.5 cm², and a mean pressure gradient of 46 mmHg. Preoperative computed tomography (CT) revealed an inverted (rightward) orientation of the ventricle apex as well as the great vessels. The TAVI was performed through a transfemoral approach under general anesthesia. A left and right reversed fluoroscopic image was used for the TAVI. Finally, a 26-mm CoreValve Evolut R (Medtronic, Minneapolis, MN, USA) was successfully deployed at the aortic annulus under angiographic guidance. Post-procedural transthoracic echocardiography demonstrated a well-functioning CoreValve Evolut R with a mean pressure gradient of 8 mmHg. No complications occurred during the procedure or peri-procedural period. The patient's symptoms subsequently improved from New York Heart Association class III to class I. In conclusion, a TAVI procedure was safely performed in a patient with dextrocardia situs inversus through a transfemoral approach by evaluating the anatomical details with preoperative CT. <Learning objective: Transcatheter aortic valve implantation (TAVI) has evolved into a standard therapy for aged patients with severe aortic valve stenosis who are not candidates for surgery. On the other hand, dextrocardia situs inversus is associated with a number of additional cardiac and vascular malformations. In this case, we report on a case in which a TAVI procedure was safely performed in a patient with dextrocardia situs inversus through a transfemoral approach.>.

Atrial electrical abnormality in patients with Brugada syndrome assessed by signal-averaged electrocardiography

BACKGROUND

Ventricular fibrillation and atrial fibrillation are well-known arrhythmias in patients with Brugada syndrome. This study evaluated the characteristics of the atrial arrhythmogenic substrate using the signal-averaged electrogram (SAECG) in patients with Brugada syndrome.

METHODS

SAECGs were performed during normal sinus rhythm in 23 normal volunteers (control group), 21 patients with paroxysmal atrial fibrillation (PAF; PAF group), and 21 with Brugada syndrome (Brugada group).

RESULTS

The filtered P wave duration (fPd) in the control, Brugada, and PAF groups was 113.9±12.9ms, 125.3±15.0ms, and 137.1±16.3ms, respectively. The fPd in the PAF group was significantly longer compared to that in the control and Brugada groups (p<0.05). The fPd in the Brugada group was significantly longer than that in the control group (p<0.05) and significantly shorter than that in the PAF group (p<0.05).

CONCLUSION

Patients with Brugada syndrome had abnormal P waves on the SAECG. The abnormal P waves on the SAECG in Brugada syndrome patients may have intermediate characteristics between control and PAF patients.

Partial left superior pulmonary vein potential elimination by an inferior ganglionated plexus ablation

Ganglionated plexus (GP) plays an important role in the initiation and maintenance of atrial fibrillation (AF). The GP ablation has been found to be effective for AF treatment. In this case, we reported an AF case in which the pulmonary vein (PV) potentials of the anterior region of the left superior PV were eliminated by an inferior right GP ablation.

Blackout during meals: A case report of swallow syncope due to sinus arrest

A 79-year-old male, with a history of percutaneous coronary intervention (PCI), was referred to our cardiovascular department for a detailed examination of blackout caused by sinus arrest only during meals. Ultrasound echocardiography showed normal cardiac contraction with no asynergy, irrespective of the remaining stenotic coronary lesion. An electrophysiological study revealed deteriorated atrioventricular nodal conduction at a Wenckebach point of 70 beats per minute. However, sinus node function was normal as demonstrated by a sinus node recovery time of 1369 ms. Coronary angiography showed triple-vessel disease including the remaining stenotic coronary lesion, and a PCI was performed on the right coronary artery. Nevertheless, sinus arrest during meals was unchanged. Swallow syncope was partially improved by dietary modification; however, pacemaker implantation (PMI) was performed eventually, and the patient became asymptomatic after PMI. <Learning objective: Swallow syncope is a rare cause of syncope that belongs to the neurally mediated reflex syncopal syndromes, which can induce a variety of bradyarrhythmias: sinus bradycardia, sinus arrest, sinoatrial block, atrioventricular block, or atrial and ventricular asystole. In this case, we demonstrated that dietary modification or pacemaker implantation improved swallow syncope due to sinus arrest.>.

Electrophysiological characteristics related to outcome after catheter ablation of idiopathic ventricular arrhythmia originating from the papillary muscle in the left ventricle

BACKGROUND AND OBJECTIVES

The electrophysiological properties associated with favorable outcome of radiofrequency catheter ablation (RFCA) for idiopathic ventricular arrhythmia (VA) originating from the papillary muscle (PM) remain unclear. The purpose of this study was to investigate the relationships of electrophysiological characteristics and predictors with the outcome of RFCA in patients with VAs originating from PM in the left ventricle (LV).

SUBJECTS AND METHODS

Twelve (4.2%) of 284 consecutive patients with idiopathic VAs originating from LV PM were assessed. The electrophysiological data were compared between the patients in the successful group and patients in the recurrence group after RFCA.

RESULTS

In 12 patients with PM VAs, non-sustained ventricular tachycardias (VTs, n=6), sustained VTs (n=4) and premature ventricular complexes (n=2) were identified as the presenting arrhythmias. Seven of eight patients showing high-amplitude discrete potentials at the ablation site had a successful outcome (85.7%), while the remaining four patients who showed low-amplitude fractionated potentials at the ablation site experienced VA recurrence. The mean duration from onset to peak downstroke (Δt) on the unipolar electrogram was significantly longer in the successful group than in the recurrence group (58±8 ms vs. 37±9 ms, p=0.04). A slow downstroke >50 ms of the initial Q wave on the unipolar electrogram at ablation sites was also significantly associated with successful outcome (85.7% vs. 25.0%, p=0.03).

CONCLUSION

In PM VAs, the high-amplitude discrete potentials before QRS and slow downstroke of the initial Q wave on the unipolar electrogram at ablation sites were related to favorable outcome after RFCA.

Long-term results of pulmonary vein antrum isolation in patients with atrial fibrillation: an analysis in regards to substrates and pulmonary vein reconnections

AIMS

To examine the impact of left atrial (LA) low-voltage zones (LVZs) on atrial fibrillation (AF) recurrence after pulmonary vein antrum isolation (PVAI) without LA substrate modification.

METHODS AND RESULTS

Seventy-six patients with AF (paroxysmal/persistent 65/11) were prospectively enroled. Left atrial voltage maps were constructed during sinus rhythm using NavX to identify LVZs (<0.5 mV), and PVAI without any LA substrate modification was performed using an open-irrigation catheter. After PVAI, 20 mg of adenosine triphosphate (ATP) was injected. Adenosine triphosphate-induced PV reconnections were eliminated by touch-up ablation when unmasked. Voltage maps revealed LVZs in 24 patients (32%) and no LVZs in 52 (68%). During 24 ± 7 months of follow-up, 15 patients (63%) with LVZs and 10 (19%) without had AF recurrences off antiarrhythmic drugs (log-rank P < 0.001). A multivariate logistic regression analysis revealed that LVZ areas [odds ratio (OR): 1.12 per 1 cm(2), 95% confidence interval (CI): 1.04-1.23, P = 0.001] and ATP-induced reconnection (OR: 2.08, 95% CI: 1.01-4.91, P = 0.046) were significant predictors of recurrence. In those with LVZs, the LVZ area was strongly correlated with the LA body volume (r = 0.81, P < 0.001) and a unique predictor of recurrence (OR: 1.17 per 1 cm(2), 95% CI: 1.01-1.55, P = 0.031), while in those without an LVZ, ATP-induced PV reconnection was a unique predictor (OR: 3.24, 95% CI: 1.15-15.39, P = 0.025).

CONCLUSION

The LVZ area was an independent predictor of recurrence after PVAI without any LA substrate modification. Adenosine triphosphate-induced PV reconnection was also an independent predictor, especially in those without LVZs.

Ventricular pacing inhibition by oversensing due to diaphragmatic myopotential during deep inspiration

An 80-year-old man, who had dilated cardiomyopathy with right ventricular (RV) dilatation, underwent implantable cardioverter defibrillator (ICD) implantation for advanced atrioventricular block and primary prevention of sudden cardiac death. Tined and screw-in leads were placed on the right atrial appendage and RV apex, respectively. Ventricular pacing inhibition was detected after surgery due to oversensing by diaphragmatic myopotential occurring only during deep inspiration. We performed re-surgery and switched the screw-in lead for a tined lead. The diaphragmatic myopotential decreased, thereby improving oversensing by diaphragmatic myopotential and ventricular pacing inhibition. It might be beneficial to use a tined lead when placing the ventricular lead at the RV apex for implantation of a pacemaker or ICD if oversensing of diaphragmatic myopotential is observed using a screw-in lead. <Learning objective: Oversensing due to diaphragmatic myopotential is rarely observed. However if it occurs, it becomes a critical problem, which causes pacemaker inhibition or inappropriate ICD shock. However, the method of preventing this problem is unknown. In this case, we demonstrated that a tined-lead may be useful for the prevention of oversensing by diaphragmatic myopotential.>.

Clinical significance of early recurrences of atrial tachycardia after atrial fibrillation ablation

BACKGROUND

atrial tachycardia (AT) commonly recurs within 3 months after radiofrequency catheter ablation for atrial fibrillation (AF). However, it remains unclear whether early recurrence of atrial tachycardia (ERAT) predicts late recurrence of AF or AT.

METHODS

of 352 consecutive patients who underwent circumferential pulmonary vein isolation with or without linear ablation(s) for AF, 56 patients (15.9%) with ERAT were identified by retrospective analysis. ERAT was defined as early relapse of AT within a 3-month blanking period after ablation.

RESULTS

during 21.7 ± 12.5 months, the rate of late recurrence was higher in patients with ERAT (41.1%) compared with those without ERAT (11.8%, P < 0.001). In a multivariable model, positive inducibility of AF or AT immediately after ablation (65.2% vs 36.4%, P = 0.046; odd ratio, 3.9; 95% confidence interval, 1.0-14.6) and the number of patients who underwent cavotricuspid isthmus (CTI) ablation (73.9% vs 42.4%, P = 0.042; odd ratio, 4.5; 95% confidence interval, 1.1-19.5) were significantly related to late recurrence in the ERAT group. The duration of ablation (174.3 ± 62.3 vs 114.7 ± 39.5 minutes, P = 0.046) and the procedure time (329.3 ± 83.4 vs 279.2 ± 79.7 minutes, P = 0.027) were significantly longer in patients with late recurrence than in those without late recurrence following ERAT.

CONCLUSIONS

the late recurrence rate is higher in the patients with ERAT compared with those without ERAT following AF ablation, and is more often noted in the patients who underwent CTI ablation and had a prolonged procedure time. Furthermore, inducibility of AF or AT immediately after ablation independently predicts late recurrence in patients with ERAT.

A new method of a pulmonary vein map to identify a conduction gap on the pulmonary vein antrum ablation line

BACKGROUND

Electrical isolation of the pulmonary veins (PV) is crucial for atrial fibrillation (AF) ablation. Conduction gaps on the circumferential PV antrum ablation (CPVA) line sometimes remain, which are sometimes difficult to identify.

METHODS AND RESULTS

CPVA of the ipsilateral superior and inferior PVs was performed during sinus rhythm or coronary sinus pacing using the NavX system in 22 AF patients, in whom 1 round of CPVA failed to disconnect 26 individual PVs (30%) in 18 patients. In these patients, a local activation map within the CPVA line (PV map) was created by a 20-pole circular mapping catheter with the use of the NavX, with 71 ± 37 sampling points per PV antrum. The conduction gap was defined as a site on the CPVA line, from which the activation proceeded toward the entire PV. The mapped PV antra were comprised of the left superior PV in 11, right superior PV in 10, left inferior PV in 3, right inferior PV in 1 and a left common PV in 1 PV(s). The conduction gaps were identified at 1.4 ± 0.7 sites per PV antrum, with an electrogram amplitude of 0.8 ± 0.7 mV. A point ablation at the gap completely isolated 24 out of 26 PV antra (92%) with 1.9 ± 1.3 applications.

CONCLUSIONS

The PV map was useful for quickly and accurately identifying the conduction gap(s) after 1 round of CPVA.

Characterization of bipolar electrograms during sinus rhythm for complex fractionated atrial electrograms recorded in patients with paroxysmal and persistent atrial fibrillation

AIMS

Complex fractionated atrial electrogram (CFAE) has been reported to relate to maintain atrial fibrillation (AF). The aims of this study were to investigate the relationship between CFAE and background conditions during sinus rhythm (SR).

METHODS AND RESULTS

Electroanatomical mapping using an EnSite Array was performed in 20 patients (paroxysmal AF:persistent AF = 16:4) who underwent pulmonary vein antrum isolation (PVAI). Contact bipolar electrograms were recorded before PVAI, during SR, and subsequently during induced AF. Peak-to-peak voltages and morphologies of the electrograms during SR were compared between sites with and without CFAE during AF. Among 1947 points obtained during SR, 974 (50%) were included in CFAE sites and 973 (50%) in non-CFAE sites. Electrogram amplitude during SR was higher at the CFAE sites than at the non-CFAE sites (2.4 +/- 1.7 vs. 1.9 +/- 1.9 mV; P < 0.0001), whereas fractionated or double electrograms were found in a similar range between the two areas (2 vs. 3%; P = 0.21). When analysed further in terms of AF termination by PVAI followed by confirmation of non-inducibility, the voltage of electrograms at the CFAE sites was lower (2.1 +/- 1.7 vs. 2.6 +/- 1.8 mV; P = 0.0001) and the morphology was more complex in patients without AF termination compared with those with AF termination.

CONCLUSION

Our results suggest that in paroxysmal and persistent AF with minimally damaged LA, the CFAE sites in patients with AF termination by PVAI alone represent healthy atrial tissue with rapid electrical activity in response to an AF driver located in the pulmonary vein. However, in patients without AF termination, they represent more damaged tissue responsible for maintaining AF.

[Antiviral effect of (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl) cytosine on adenovirus]

PURPOSE

Adenovirus is the most frequent causative virus of conjunctivitis in Japan. Recently (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl) cytosine (HPMPC) has been promoted as a new drug against adenoviral conjunctivitis. So we examined the antiviral activity of HPMPC against adenoviruses in vitro.

METHOD

The antiviral activity of HPMPC against adenovirus (Ad) type 3, type 4, type 19, and type 37 isolated from conjunctivial scrapings in Japan and the prototype of adenovirus type 5 was examined by plaque reduction assay using A 549 cells in vitro.

RESULTS

The 50% inhibitory dose (ID50) of HP-MPC was 3.50 (1.44-4.79) micrograms/ml for Ad type 3, 4.50 (4.17-4.92) micrograms/ml for Ad type 4, 2.11 (1.03-3.13) micrograms/ml for Ad type 5, 1.64 (1.40-2.02) micrograms/ml for Ad type 19, and 2.02 (1.17-2.73) micrograms/ml for type 37. The 50% cytotoxic dose of HPMPC for A 549 cells was 205 micrograms/ml by the deoxythimidine uptake inhibition test, and 537 micrograms/ml by the trypan blue exclusion inhibition test.

CONCLUSIONS

HPMPC proved to be highly effective in inhibiting replication of adenoviruses at lower concentrations than the cytotoxic level in vitro.

Effects of lidocaine and diltiazem on ventricular tachyarrhythmia and dispersion of conduction during severe myocardial ischemia in canine hearts

The purpose of this study was to investigate the effects of lidocaine and diltiazem on ventricular tachyarrhythmia and dispersion of conduction during severe myocardial ischemia in dogs. Myocardial ischemia was produced by a 10-min occlusion of the left anterior descending artery by the retrograde blood flow technique. Saline, lidocaine, and diltiazem were infused intravenously before and during occlusion in groups A (n = 16), B (n = 22) and C (n = 13), respectively. The incidence of ventricular tachycardia (VT) consisting of ten or more VPC was 19% in group A, 73% in group B and 31% in group C (A vs. B, P < 0.01), and that of ventricular fibrillation (VF) was 31%, 64%, and 15%, respectively (A vs. B, P < 0.05). The time of the onset of VT preceding VF was shorter in group B than in group A (207.9 +/- 13.9 vs. 353.2 +/- 70.7 sec, P < 0.05). The time taken to reach maximal dispersion of conduction delay in the epicardium was shorter in group B than in group A (192.1 +/- 11.9 vs. 337.5 +/- 38.2 sec, P < 0.01), and the dispersion of conduction delay in the intramyocardial layers was smaller in group B than in group A (229.9 +/- 24.5 vs. 360.0 +/- 35.6 sec, P < 0.01). The time taken to reach maximal dispersion of conduction delay in the endocardium was greater in group C than in group A (400.8 +/- 38.8 vs. 274.4 +/- 23.9 sec, P < 0.01). However, there were no significant differences among the three groups with regard to the maximal dispersion of conduction delay in the epicardium, in the endocardium, or intramyocardial layer. These results suggest that lidocaine increased ventricular tachyarrhythmia due to an acute increase in dispersion of conduction in the epicardium and intramural layer, and that diltiazem was not effective in preventing ventricular tachyarrhythmia and did not affect the dispersion of conduction in the epicardium or intramural layer despite improvement in the endocardium.

Effects of ischemic preconditioning on ventricular arrhythmias during ischemia and reperfusion using a retrograde blood flow model in dogs

We examined the effects of ischemic preconditioning on ventricular arrhythmias during ischemia and reperfusion from the electrophysiologic point of view by using the retrograde blood flow (RBF) model, which causes severe ischemia. A total of 51 anesthetized dogs were divided into 3 groups. Group 1 (10-min simple occlusion) consisted of 15 dogs; group 2 (10-min RBF) consisted of 20 dogs; and group 3 (10-min RBF with preconditioning) consisted of 16 dogs. Preconditioning consisted of 5 cycles of 2 min of ischemia (RBF) and 5 min of reperfusion. In the subepicardium, myocardial blood flow (MBF) in group 2 was significantly lower than in group 1 or group 3 [group 2 (4.7 +/- 2.3 ml/min per 100 g) vs group 1 (35.0 +/- 5.8) or group 3 (22.0 +/- 4.6); p < 0.01 and p < 0.05 respectively]. However, there were no differences in MBF in the subendocardium between the 3 groups. The incidence of conduction block in the subepicardium was significantly higher in group 2 than in group 1 or group 3 [group 2 (85%) vs group 1 (33%), p < 0.01; vs group 3 (38%), p < 0.01]. There were no differences in the incidence of conduction block in the subendocardium between the 3 groups. During 10-min ischemia, the incidences of ventricular fibrillation (VF) were 7% in group 1, 35% in group 2, and 6% in group 3 (group 2 vs group 1, p < 0.05; and group 2 vs group 3, p < 0.05). During 10-min reperfusion, the incidences of VF were 29% in group 1, 77% in group 2, and 33% in group 3 (group 2 vs group 1, p < 0.05; and group 2 vs group 3, p < 0.05). Ventricular arrhythmias were reduced during both 10-min ischemia and 10-min reperfusion as a result of the improvement in the conduction components by ischemic preconditioning which increased MBF in the subepicardium.

Effects of lidocaine and diltiazem on recovery of electrophysiologic activity during partial reperfusion following severe myocardial ischemia in canine hearts

The effects of lidocaine and diltiazem on recovery of electrophysiologic activity during partial reperfusion following severe myocardial ischemia were investigated in 28 dogs. The left anterior descending artery was ligated, and the distal end was connected to the carotid artery. Myocardial ischemia was induced by retrograde blood flow for 10 minutes, after which flow-limited reperfusion (30-60% of the coronary flow before ischemia) was performed. The dogs were divided according to the agent administered before ischemia into the following three groups: saline (group S, n = 11); lidocaine (group L, n = 8, 0.07 mg/kg/min by intravenous drip infusion following 2 mg/kg intravenous injection); and diltiazem (group D, n = 9, 0.02 mg/kg/min by intravenous drip infusion. There were no significant differences among the three groups in the incidence of ventricular tachyarrhythmia, which occurred as ventricular tachycardia (VT) or ventricular fibrillation (VF). In each group, the occurrence of VT was frequently preceded by delayed potential which was initiated after reperfusion, with depressed conduction in the epicardium, suggesting reentry (82%, 96%, and 87%, not significant). The determining factors for VT with degeneration into VF were long duration of VT in groups S and L (VT with degeneration into VF vs VT without, 1.2 +/- 0.2 seconds vs 0.6 +/- 0.1 seconds, P < .05, in group S and 11.6 +/- 2.5 seconds vs 2.2 +/- 0.4 seconds, P < .05, in group L), and decrease in average R-R interval during VT in groups L and D (195 +/- 8 ms vs 313 +/- 17 ms, P< .01, in group L and 201 +/- 11 ms vs 327 +/- 28 ms, P< 0.01, in group D). In addition, occurrence of epicardial electrophysiologic activity with reduced time from onset of the QRS complex in the surface electrocardiogram to the onset of the activity during VT preceded VF in group L (VT with degeneration into VF vs VT without, 130.0 +/- 15.1 ms vs 185.8 +/- 21.4 ms, P < .05), while that with prolongation of the time had this effect in group D (116.0 +/- 15.7 ms vs 69.0 +/- 10.7 ms, P < .05). It is concluded that, even when partial reperfusion is applied, neither lidocaine nor diltiazem suppresses VT because neither drug decreases delayed potential acting as a triggering factor or suppresses VF, since the alteration of the epicardial conductivity during VT can change the VT circuit to a smaller one.

[Rapid detection and identification of human adenovirus directly from conjunctival scrapings by polymerase chain reaction and restriction fragment length polymorphism analysis]

Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis were combined for detection and identification of adenovirus (Ad), a common agent of conjunctivitis in Japan. Nested-PCR with two primer sets that hybridize to the conserved region for hexon protein of 14 prototypes of Ad serotype 1 to 8, 11, 14, 19, 37, 40, and 41, amplified 956 bps DNA fragment. The amplified fragments from 14 prototypes were completely differentiated with the combination of three restriction endonucleases, Eco T14I, Hae III, and Hin fI. We applied this new method to 70 conjunctival scrapings from patients with conjunctivitis, and compared the results with those of the combination of culture isolation and neutralization test. PCR was positive in 38 out of 70 samples (54.3%), whereas 33 of 70 samples (47.1%) were positive by cell culture. Compared with cell culture isolation, the PCR method had a sensitivity of 100% (33 of 33). Positive PCR samples were further classified into Ad 37 (44.7%), 3 (39.5%), 11 (7.9%), 8 (5.3%), and 4 (2.6%) by PCR-RFLP analysis. Of five samples that were PCR positive and cell culture negative, three samples were Ad 37 and two were Ad 8 by PCR-RFLP analysis. These differentiations of cell culture positive samples were identical to the results of the neutralization test. It took only about three days to detect and identify Ad by PCR-RFLP analysis, whereas it took at least two weeks by culture isolation and neutralization test. Our newly developed method of detecting and typing human Ad by PCR-RFLP analysis is more sensitive, accurate, and prompt than the conventional cell culture isolation and neutralization test.

Electrophysiologic changes before onset of ventricular tachyarrhythmias during partial reperfusion following severe myocardial ischemia in dogs

We examined the electrophysiologic changes before an onset of ventricular tachyarrhythmia during partial reperfusion following severe myocardial ischemia. The left anterior descending coronary artery was occluded and cannulated below the occluded portion in 26 dogs. To deplete collateral flow into the ischemic myocardium, retrograde blood flow was induced for 20 min. Then, in all dogs except 7 with ventricular fibrillation during retrograde blood flow, partial reperfusion through collateral flow into the ischemic myocardium was produced by stopping the retrograde flow. Within 2 min of partial reperfusion, sustained ventricular tachycardia (VT) occurred in 7 dogs (group A) and non-sustained VT degenerating ventricular fibrillation occurred in 11 dogs (group B) of the remaining 12 dogs. In 6 dogs of group A and 9 of group B, epicardial conduction block appeared 5.0 +/- 2.2 and 3.5 +/- 1.3 min after ischemia. This was followed by fractionated electrical activities 15.2 +/- 3.2 and 11.7 +/- 3.3 min after ischemia. In group A, the fractionation had a slight change in configuration and a small increase in amplitude before the onset of VT during reperfusion; in group B, new deflections with large amplitude emerged before it. There was a significant difference in the amplitude (0.38 +/- 0.2 vs 0.67 +/- 0.3 mV, p < 0.025) between the 2 groups, although there was no significant difference in the amplitude (0.33 +/- 0.2 vs 0.23 +/- 0.1 mV) of the fractionation just before reperfusion. Our results show that slight improvement in fractionation induces sustained VT, and new deflections induce non-sustained VT degenerating ventricular fibrillation, even during partial reperfusion.

Double atrial response to a single ventricular extrastimulus in a patient with Wolff-Parkinson-White syndrome

Electrophysiological examination in a 39-year-old male disclosed an accessory pathway between the right atrium and the right ventricle and AV nodal dual pathways. Atrial and ventricular extrastimuli induced paroxysmal supraventricular tachycardia (PSVT), which was shown to be AV reciprocating tachycardia. Double atrial response was noted during ventricular extrastimuli at V1V2 of 280 msec and V1V2 of 250 msec. The first atrial response is considered to have been transmitted in a retrograde fashion in the accessory pathway, and the second atrial response similarly in the slow pathway of the AV node.

Myocardial blood flow, alternans of ST segment elevation, conduction delay and ventricular arrhythmia during acute myocardial ischemia with and without retrograde blood flow in canine hearts

The technique of retrograde blood flow has been shown to decrease collateral flow into the ischemic myocardium, and to cause severe myocardial ischemia in dogs. Ischemia with retrograde blood flow in dogs is similar to ischemia in human hearts. Therefore, we examined the effect of retrograde blood flow on myocardial blood flow, ST segment elevation, alternans of ST segment elevation, conduction delay and ventricular arrhythmia in dogs. Sixty dogs were divided into two groups. In group A (N = 32), the left anterior descending coronary artery was occluded for 10 min. In group B (n = 28), ischemia was induced by the technique of retrograde blood flow for 10 min. During ischemia, the myocardial blood flow at the ischemic zone measured by a H2 gas clearance method was 11.2 +/- 1.6 in group A and 5.7 +/- 0.7 ml/min/100 g in group B (p less than 0.01). The maximal ST segment elevation was 13.6 +/- 1.9 in group A and 27.2 +/- 2.1 mV in group B (p less than 0.001); the maximal alternans of ST segment elevation was 5.3 +/- 1.1 in group A and 10.1 +/- 1.4 mV in group B (p less than 0.01); the maximal conduction delay was 51.6 +/- 8.4 in group A and 111.1 +/- 6.2 msec in group B (p less than 0.001); and the incidences of ventricular premature beats (greater than 5/min), ventricular tachycardia and fibrillation were 34%, 41% and 22% in group A, and 68%, 79% and 25% in group B (p less than 0.01, p less than 0.01 and not significant, respectively). It is concluded that ischemia with retrograde blood flow can be used to examine occlusive and reperfusion ventricular arrhythmia in dogs, because the incidences of ventricular premature beats and ventricular tachycardia were high, but that of ventricular fibrillation was not high despite the severe ischemia.

Reflection as a cause of mid-systolic deceleration of pulmonary flow wave in dogs with acute pulmonary hypertension: comparison of pulmonary artery constriction with pulmonary embolisation

STUDY OBJECTIVE

The aim was to examine whether mid-systolic deceleration of the pulmonary flow wave occurred in acute pulmonary hypertension due to pulmonary artery constriction and pulmonary embolisation, and if so whether it was related to reflection.

DESIGN

Various degrees of pulmonary hypertension were induced by both pulmonary artery constriction and pulmonary embolisation in dogs. During control periods and during pulmonary artery constriction and pulmonary embolisation, pulmonary flow and pulmonary artery pressure were recorded, and the forward and backward (reflected) flow waves were separated from the measured pulmonary flow wave by the method of Westerhof et al.

MATERIALS

20 adult mongrel dogs were used and 10 dogs qualified for analysis. The other 10 dogs, which died before both interventions were completed, were excluded.

MEASUREMENTS AND MAIN RESULTS

During pulmonary artery constriction, a distinct mid-systolic deceleration of the pulmonary flow wave was observed in five of the 10 dogs, while during pulmonary embolisation, no mid-systolic deceleration was found in these five dogs. The distinct deceleration of the pulmonary flow wave was related to a steep fall and early negative peak in the backward flow wave.

CONCLUSION

Mid-systolic deceleration of pulmonary flow wave is likely to be related to reflection.

Effect of pre-existing four hour coronary stenosis on ventricular arrhythmias during a subsequent 10 minute occlusion in dogs

STUDY OBJECTIVES

The aim was to assess the effect of pre-existing coronary stenosis on ventricular arrhythmia during subsequent acute coronary occlusion.

DESIGN

Dogs with a 4 h intact interval followed by a 10 min occlusion of left anterior descending coronary artery (group A) were compared for ventricular arrhythmias with dogs with a 4 h stenosis of the same artery followed by a 10 min occlusion (group B). Myocardial blood flow was measured in the ischaemic myocardium using the H2 gas clearance method to exclude dogs with good collateral flow (myocardial blood flow greater than 11.0 ml.min-1.100g-1).

EXPERIMENTAL ANIMALS

35 mongrel dogs of either sex, weight range 11-26 kg, were used in the experiments (group A, n = 17; group B, n = 18). After exclusion of dogs with good collateral circulation there were 11 dogs in group A (subgroup A1) and 12 dogs in group B (subgroup B1).

MEASUREMENTS AND MAIN RESULTS

The incidence of ventricular fibrillation was lower in group B (pre-existing stenosis) than in group A during the 10 min occlusion, though there was no difference in numbers of ventricular premature beats. Maximum ST segment elevation and maximum conduction delay were less in group B than in group A, but myocardial blood flow did not differ during the 10 min occlusion. In the subgroups the incidence of both types of ventricular arrhythmia was lower in subgroup B1 during the 10 min occlusion, while the maximum ST segment elevation and maximum conduction delay were less, and myocardial blood flow was greater.

CONCLUSIONS

Pre-existing 4 h coronary stenosis causes the development of collateral flow and reduces the incidence of ventricular arrhythmias during subsequent occlusion.

Ventricular fibrillation during partial reperfusion following severe myocardial ischemia in the canine model

The authors examined whether partial reperfusion protects against reperfusion ventricular fibrillation (VF) following severe acute myocardial ischemia. Fifty-seven dogs were divided into two groups. In group A (n = 21), the left anterior descending coronary artery was occluded for 10 minutes, followed by full reperfusion. In the remaining 36 dogs (group B), myocardial ischemia was induced by retrograde blood flow (RBF) for 10 minutes. Thereafter, these dogs were divided into three subgroups: in group B1 (n = 10), full reperfusion was made by a carotid-left anterior descending coronary artery bypass; in group B2 (n = 13), partial reperfusion was achieved by collateral flow into the ischemic zone due to stopping RBF; in group B3 (n = 13), RBF was continued for an additional 5 minutes. During 10 minute ischemia, the myocardial blood flow at the ischemic zone measured by the H2 gas-clearance method was 12.3 +/- 2.0 ml/min/100 g in A, 3.4 +/- 0.9 ml/min/100 g in B1, 4.7 +/- 0.6 ml/min/100 g in B2, and 4.7 +/- 0.6 ml/min/100 g in B3 (A vs B1, p less than 0.02; A vs B2 and B3, p less than 0.01). Maximal ST-segment elevation was 11.4 +/- 1.8 mV in A, 28.2 +/- 2.7 mV in B1, 25.1 +/- 3.0 mV in B2, and 27.0 +/- 1.9 mV in B3 (A vs B1, B2, and B3, p less than 0.001). Maximal conduction delay was 48.6 +/- 9.4 ms in A, 106.4 +/- 5.2 ms in B1, 101.6 +/- 9.9 ms in B2, and 91.2 +/- 5.1 ms in B3 (A vs B1, B2, and B3, p less than 0.001). The incidence of reperfusion VF was 14% (3/21) in A, 80% (8/10) in B1, and 69% (9/13) in B2 (A vs B1, p less than 0.001; A vs B2, p less than 0.005). In group B3, VF occurred in only 1 of 13 dogs for the additional 5 minutes. It is concluded that reperfusion VF occurred frequently when ischemia was severe even though the duration of ischemia was short (B1), and that reperfusion VF was not prevented by partial reperfusion when the ischemia was severe (B2).

Relationship of alternans of monophasic action potential and conduction delay inside the ischemic border zone to serious ventricular arrhythmia during acute myocardial ischemia in dogs

We studied the relationship of conduction delay and monophasic action potential (MAP) at an ischemic border zone to serious ventricular arrhythmia (VA). Measurements were made in 36 adult mongrel dogs 15 minutes after occlusion of the left anterior descending coronary artery. We recorded MAPs and bipolar electrograms simultaneously inside and outside the ischemic border zone in the dog hearts. Of the 36 dogs, 24 that had favorable MAP recordings were chosen and were divided into two groups according to an occurrence of VA. In group A (n = 12), an onset time of VA was 5.1 +/- 0.8 minutes after ischemia, while in group B (n = 12) VA did not occur during ischemia. The conduction delay at the ischemic border zone was significantly greater from 3 minutes after ischemia in group A than in group B. MAP alternans, defined as the difference in duration of two consecutive MAPs inside the ischemic border, was marked in group A but mild in group B. Duration of a small MAP of alternans was markedly shorter than that of a corresponding MAP outside the ischemic border in both groups, but was followed by VA in group A. Duration of a large MAP was markedly prolonged compared with that of a corresponding MAP outside the ischemic border in seven dogs of group A and in only one dog of group B (p less than 0.01), and was followed by VA in seven dogs of group A. Our results suggest that the mechanism of VA is due not only to reentry but also to an injury current flowing from ischemic to nonischemic tissues, because VA was preceded by conduction delay and by a difference in MAP durations when comparing regions inside and outside the ischemic border.

[A case of intermittent ventricular pre-excitation syndrome with a Mahaim fiber]

A 61 year-old woman with intermittent ventricular pre-excitation syndrome using a Mahaim fiber was reported. The electrocardiogram showed QRS-complex with small delta wave (100 msec in QRS width) or without small delta wave (80 msec in QRS width). On electrophysiological study, during sinus rhythm, A-H interval was 100 msec. H-V intervals were 25 msec in QRS-complex with small delta wave and 45 msec in QRS-complex without small delta wave. From these findings, it was considered that the small delta wave was produced by a Mahaim fiber.