Supraventricular arrhythmias limit effective cardiac resynchronization therapy: Diagnosis using intracardiac electrograms and device based pacing maneuvers

Cardiac resynchronization therapy is an effective tool for the treatment of drug-refractory heart failure in patients with left ventricular dysfunction and inter/intra ventricular conduction delay. Supraventricular tachycardias may prevent effect delivery of this therapy. We report three cases in which effective therapy was limited by asymptomatic supraventricular tachycardia. Diagnostic pacing maneuvers were performed via the implanted device to determine the underlying arrhythmia mechanism. These cases highlight the importance of (1) treating supraventricular tachycardias before and after implantation of cardiac devices and (2) using device based programmed stimulation to diagnose the mechanism of supraventricular tachycardias. Dr. Gerstenfeld is supported by a Scientist Development Grant from the American Heart Association.     

Identification of successful catheter ablation sites in patients with ventricular tachycardia based on electrogram characteristics during sinus rhythm

BACKGROUND: Zones of slow conduction facilitate reentry, the major mechanism of ventricular tachycardia (VT) after myocardial infarction (MI). Identification of these zones during sinus rhythm (SR) is desirable for radiofrequency (RF) catheter ablation of VT. Local conduction velocity may correlate with electrogram duration. OBJECTIVES: The purpose of this study was to revise the definition of normal electrogram characteristics and to reevaluate the significance of low-amplitude, long-duration electrograms recorded during SR to select RF catheter ablation sites in patients with VT. METHODS: Electroanatomic mapping was performed during SR in 10 control patients with normal left ventricles (LVs) and in 10 patients with stable VT after MI. From the controls, reference values for electrogram amplitude, duration (first peak to last peak distance), and fragmentation (positive deflection) were derived. In patients after MI, areas with signals exceeding these values were annotated and related to successful ablation sites. RESULTS: Ninety-five percent of normal LV electrograms were > or =1.0 mV and < or =28 ms (range 5-39 ms) and all had < or =4 deflections. Based on these results, cutoff values were set at 1 mV, four deflections, and 40 ms. In infarcted hearts, 653 electrograms (44%) were <1.0 mV and of these, 303 were > or =40 ms with >4 deflections and restricted to circumscribed areas. Twenty-seven of 28 targeted VTs remained noninducible after RF catheter ablation within these areas, resulting in 86% sensitivity and 94% specificity for low-amplitude, long-duration electrograms predicting successful ablation sites. CONCLUSION: Identification of successful RF target areas during SR in patients with VT is feasible with high sensitivity and specificity using a mapping strategy based on voltage and duration criteria.     

阵发性心房颤动患者心脏大静脉肌袖电活动特征的临床研究

总结和探讨阵发性心房颤动(简称房颤)患者心内电生理标测中肺静脉和上腔静脉内肌袖电活动的特征,及其与房颤的关系。选择无器质性心脏病的顽固性阵发性房颤患者 126例,用环状标测电极行肺静脉和 /或上腔静脉电生理标测,分析引起房性心律失常时肌袖内的电活动类型、频率、发作方式及其与房颤之间的联系。结果:有50例(39. 7% )经心电生理标测证实其房性心律失常与大静脉肌袖的自发电活动相关。共标测心脏大静脉 354根,心律失常相关大静脉 59根,包括肺静脉 49根、上腔静脉 10根。电活动类型呈现单一或连发电活动 38根,呈短阵性快速电活动 8根,呈连续快速( >300次 /分)电活动 27根,呈连续较慢电活动 ( <100次 /分 ) 2根。房颤的发生均与静脉肌袖内连续快速的、规律或紊乱的电活动对心房的引发有关。结论:根据房性心律失常发作时的大静脉肌袖内电位的特征以及与心房电位的关系,可以明确判定房颤的相关肌袖。同一根大静脉肌袖可表现为 2种或 2种以上的电活动类型,其中以单一和连续快速电活动多见,房颤均为静脉肌袖内的连续快速电活动所引发,而非单一房性早搏诱发。     

典型心房扑动射频消融术后发生心房颤动患者的心房电生理特性

分析典型心房扑动(简称房扑)射频消融术后发生心房颤动(简称房颤)患者的心房电生理特性,探讨心房内传导时间在房颤发生中的意义。56例典型房扑患者,其中19例有器质性心脏病,16例在消融前有房颤发作。所有患者均进行常规的电生理检查及标测,记录消融前后心房的电生理参数。根据消融术后随访是否有房颤的发生分为两组进行分析。结果:56例房扑患者全部消融成功,随访14±12(6～60)个月,中位数14个月。消融术后15例有房颤发作,其中3例进展为慢性房颤。15例有房颤发作患者的年龄较无房颤发作的患者大(57.1±13.6岁vs42.3±11.2岁,P<0.05),消融术前和术后的高右房至冠状窦的传导时间延长(分别为98.4±17.1msvs67.8±16.5ms;93.1±18.4msvs70.2±19.7ms;P均<0.05)。多因素Cox回归分析消融前有房颤发作的病史(危险比2.3,95%CI1.425～4.632,P=0.02)和窦性心律下高右房至冠状窦的传导时间超过90ms(危险比1.7,95%CI1.215～3.758,P=0.03)是预测射频消融术后发生房颤的独立的危险因素。结论:典型房扑射频消融术后发生房颤患者心房内传导延迟,并且房内传导延迟是预测射频消融术后发生房颤的重要电生理指标。     

预激综合征旁道的心电图、心脏标测定位(附六例报告)

对6例预激综合征旁道进行心电图、电生理检查及心外膜标测定位和比较,结果提示综合二种心电图δ波极性作旁道定位的方法有较高的准确性。电生理检查对确定左或右旁道的存在有帮助,而作心内膜标测确定旁道位置较困难。认为显性预激综合征者,旁道切割术前不必强调作电生理检查,除非为隐匿性预激。用手指压迫预计的旁道部位,使δ波消失和/或阵发性室上性心动过速终止可能是心外膜标测的一种简便的方法。     

Ventricular fibrillation during programmed ventricular stimulation: Incidence and clinical implications

Ventricular fibrillation occurred in 10 (3.3 percent) of 300 patients consecutively studied with programmed ventricular stimulation. One hundred twenty-five of these patients were studied with double ventricular extrastimuli including 68 patients with and 57 patients without documented or suspected ventricular tachycardia or fibrillation, or both. Ventricular fibrillation did not develop in response to a single ventricular extrastimulus delivered during sinus rhythm, ventricular pacing or ventricular tachycardia or in response to ventricular pacing at cycle lengths of 300 msec or greater and occurred only in response to double ventricular extrastimuli. All 10 patients who manifested ventricular fibrillation during programmed stimulation were in the group of patients with suspected or documented ventricular tachycardia or fibrillation. Ventricular fibrillation was initiated in seven patients with double ventricular extrastimuli delivered during sinus rhythm or ventricular pacing and in three patients with double ventricular extrastimuli delivered during ventricular tachycardia. Four patients had spontaneous conversion to sinus rhythm and the remainder underwent defibrillation without sequelae. Recurrent ventricular fibrillation occurred clinically in 7 of the 10 patients. This study suggests that ventricular fibrillation occurs uncommonly during programmed ventricular stimulation and only in response to double ventricular extrastimuli in patients in whom spontaneous episodes are likely to occur.     

常规标测与球囊电极三维标测指导右室间隔部室性早搏射频消融比较

目的：比较常规电生理标测与Ensite array球囊标测指导下对特发性右室间隔部室性早搏导管射频消融的效果。方法将88例右室间隔部室早患者分为2组,39例室早采用常规电生理标测、49例室早采用Ensite array球囊标测。比较射频消融治疗时2组靶点标测时间、X线曝光时间、消融时间、手术总时间,观察随访疗效。结果与常规电生理标测相比, Ensite array 球囊标测室早靶点标测时间、X线曝光时间、消融时间、手术总时间均显著缩短（P＜0．01）;2组的即刻成功率均为100％;术后1个月随访时,常规电生理标测组有5例室早复发;Ensitearray球囊标测组有1例复发。结论 Ensitearray球囊标测可缩短手术时间、降低术后复发率。     

Dietary constituent genistein inhibits the hyperexcitability of trigeminal nociceptive neurons associated with mechanical hyperalgesia following orofacial inflammation

ObjectivesGenistein, a dietary constituent, modulates voltage-dependent and ligand-gated ionic channels, suggesting that it could also attenuate inflammatory hyperalgesia. However, the mechanism underlying how genistein affects inflammation-induced hyperexcitability of nociceptive neurons in vivo remains to be determined. The present study therefore investigated whether administration of genistein could attenuate the inflammation-induced hyperexcitability of trigeminal spinal nucleus caudalis (SpVc) neurons associated with mechanical hyperalgesia in vivo.MethodsInflammation was induced by injection of complete Freund's adjuvant into the whisker pad. The mechanical thresholds for escape behavior and electrophysiological single-unit recording of SpVc neurons responding to mechanical stimulation were then conducted in naïve rats, inflamed rats, and inflamed rats with genistein administered intraperitoneally.ResultsThe lowered mechanical threshold in the inflamed rats was returned to control level following administration of genistein for 2 days. The mean number of discharge frequencies of SpVc neurons in inflamed rats was significantly decreased after genistein administration with both non-noxious and noxious mechanical stimuli. The increased spontaneous discharges of SpVc neurons in inflamed rats were significantly decreased after genistein administration. Noxious pinch-evoked after-discharge frequency and occurrence in inflamed rats was also significantly diminished after genistein administration, and expansion of the receptive field was significantly returned to control levels in inflamed rats.ConclusionHerein, we present the first evidence that genistein attenuates hyperexcitability of SpVc neurons associated with inflammatory mechanical hyperalgesia. These findings suggest that genistein could be a potential therapeutic agent in complementary alternative medicine for the prevention of trigeminal inflammatory hyperalgesia.     

TIDAL WAVES: Network mechanisms in the neuroendocrine control of prolactin release

Neuroendocrine tuberoinfundibular dopamine (TIDA) neurons tonically inhibit pituitary release of the hormone, prolactin. Through the powerful actions of prolactin in promoting lactation and maternal behaviour while suppressing sexual drive and fertility, TIDA neurons play a key role in reproduction. We summarize insights from recent in vitro studies into the membrane properties and network behaviour of TIDA neurons including the observations that TIDA neurons exhibit a robust oscillation that is synchronized between cells and depends on intact gap junction communication. Comparisons are made with phasic firing patterns in other neuronal populations. Modulators involved in the control of lactation – including serotonin, thyrotropin-releasing hormone and prolactin itself – have been shown to change the electrical behaviour of TIDA cells. We propose that TIDA discharge mode may play a central role in tuning the amount of dopamine delivered to the pituitary and hence circulating prolactin concentrations in different reproductive states and pathological conditions.