Spectral and correlation analyses of the verapamil-induced conversion of ventricular fibrillation to tachycardia in isolated rat hearts

Ventricular tachycardia (VT) is considered to be the most common precursor of ventricular fibrillation (VF). However, the mechanisms underlying the transition from VT to VF remain unclear. Here, we investigated whether and how perfusion of the heart with verapamil, a blocker of L-type calcium channels, changed the macro-dynamics of the heart between VT and VF. The experiments were performed with Langendorff perfused isolated rat hearts, in which left ventricular pressure and left ventricular cardiomyogram were measured. Sustained VT or VF was induced by burst pacing of the left ventricular muscles. During sustained VF, verapamil perfusion resulted in the conversion of VF to VT. A cross-correlation analysis between left ventricular cardiomyogram and left ventricular pressure revealed that the correlation coefficient was small during VF, but became larger during VT. This study showed that inactivation of L-type Ca(2+) channels occurred during verapamil-induced conversion of pacing-induced sustained VF to VT, and characterized the changes in macro-dynamics of the heart associated with the transition.     

Failure in short-term prediction of ventricular tachycardia and ventricular fibrillation from continuous electrocardiogram in intensive care unit patients

Background

Patients in the intensive care unit (ICU) setting are prone to malignant ventricular arrhythmias. We sought to test whether electrocardiographic (ECG) markers of autonomic tone, ventricular irritability, and repolarization lability could be used in short-term prediction of ventricular arrhythmias in this patient population.

Methods

We studied 38 patients with sustained (>30 seconds) monomorphic ventricular tachycardia, polymorphic ventricular tachycardia, or ventricular fibrillation while monitored in the ICU and 30 patients without arrhythmia in the ICU who served as controls. All patients had at least 12 hours of continuously recorded multilead ECG before arrhythmic event. Mean heart rate and measures of heart rate variability, QT variability, and ventricular ectopy were quantified in 1-hour epochs for the 12 hours before the arrhythmic event and in 5-minute epochs for the last hour preevent (and using a random termination time point in controls).

Results

A modest downward trend in QT variability and a rise in heart rate were observed hours before polymorphic ventricular tachycardia and ventricular fibrillation events, although no significant changes heralded monomorphic ventricular tachycardia and no changes in any parameter predicted imminent ventricular arrhythmia of any type. There were no significant differences in ECG parameters between arrhythmia patients and controls.

Conclusions

In ICU patients, sustained ventricular arrhythmias are not preceded by change in ECG measures of autonomic tone, repolarization variability, and ventricular ectopy. Short-term arrhythmia prediction may be difficult or impossible in this patient population based on ECG measures alone.     

Spatially discordant voltage alternans cause wavebreaks in ventricular fibrillation

BACKGROUND: Ventricular fibrillation (VF) is characterized by complex ECG patterns emanating from multiple, short-lived, reentrant electrical waves. The incessant breakup and creation of new daughter waves (wavebreaks) perpetuate VF. Dispersion of refractoriness (static or dynamic) has been implicated as a mechanism underlying wavebreaks. OBJECTIVE: The purpose of this study was to investigate the mechanisms underlying wavefront instability in VF by localizing wave fractionation sites (the appearance of multiple waves) and their relationship to local spatial dispersion of voltage (V(m)) oscillations. METHODS: Wave fractionations were identified by tracking V(m) oscillations optically at unprecedented spatial (100 x 100 pixels) and temporal (2,000 frames per second) resolution using a CMOS camera viewing the surface (1 x 1 cm(2)) of perfused guinea pig hearts (n = 6). VF was induced by burst stimulation, and wavefront dynamics were highlighted using region-based image analysis to automatically detect wavebreaks. Direct detection of wavebreak locations by image analysis was more reliable than the phase reconstruction method because baseline noise obstructed the correct identification of phase singularities by detecting false-positives. RESULTS: Wave fractionations (34 +/- 4 splits/s.cm(2)) fell into three categories: decremental conduction (49% +/- 7%), wave collisions (32% +/- 8%), and wavebreaks (17 +/- 2%). Wavebreaks occurred at a frequency of 5.8 +/- 1 splits/s.cm(2) and did not preferentially occur at anatomic obstacles (i.e., coronary vessels) but coincided with discordant alternans where V(m) amplitudes and durations shifted from high to low to from low to high on opposite sides of wavebreak sites. CONCLUSION: Spatial discordant alternans cause wavebreaks most likely because they are sites of abrupt dispersion of refractoriness.     

Exploring QT interval changes as a precursor to the onset of ventricular fibrillation/tachycardia

In the present study, we have retrospectively analyzed the corrected QT (QTc) interval before spontaneous episodes of sudden cardiac arrest in patients with a wearable cardioverter defibrillator. Corrected QT interval was measured for all normal beats from 32 recordings of baseline rhythm and compared to normal rhythm before a paired spontaneous cardiac arrhythmia. Before arrhythmia, the QTc (505 ± 73 ms) was not significantly longer than the baseline rhythm (497 ± 73 ms) (P = .23). Considering ventricular tachycardia (VT) events only (12 patients), event QTc (526 ± 75 ms) was not significantly longer than baseline QTc (520 ± 74 ms) (P = .41). Considering fast VT/ventricular fibrillation (VF) events only (20 patients), event QTc (494 ± 70 ms) was not significantly longer than baseline QTc (483 ± 71 ms) (P = .26). The influence of QTc as a measure to indicate an impending VT event in a variety of VT/VF patients remains unclear.     

致心律失常性右心室心肌病患者心室晚电位与室性心动过速关系

目的探讨致心律失常性右心室心肌病(arrhythmogenic right ventricular dysplasia/cardiomyopathy,ARVD/C)合并室性心动过速与心室晚电位的关系。方法ARVD/C38例,男28例,女10例,年龄(35±15)岁。心电图检查进行信号叠加,记录心室晚电位量化参数:总QRS时限(total QRS duration,QRST)、QRS终末部位电压低于40μV时限(low potential terminal signals,LPS40)、QRS最后40ms电压方根均数(root mean square of the last 40 ms,RMS40);动态心电图检查记录室性心动过速和室性期前收缩。使用χ2及Mann-Whitney秩和检验统计。结果①心室晚电位阳性25例,其中室性心动过速18例;心室晚电位阴性13例,室性心动过速3例(P=0.004);②室性心动过速阳性21例,阴性17例,QRST:室性心动过速阳性组109～233(中位数147)ms,阴性组85～158(中位数104)ms(P=0.000);LPS40:阳性组15～158(中位数53)ms和阴性...     

特发性右室流出道室性早搏触发多形性室性心动过速或心室颤动四例的临床特点

目的报道4例特发性右室流出道(RVOT)室性早搏(PVC)触发多形性室性心动过速/心室颤动(PVT/VF)的临床特点。方法 76例起源于RVOT的VT患者,其中4例为PVC触发PVT/VF,总结4例的临床资料并与另72例有关资料相比较。结果所有4例触发PVT/VF时的PVC与孤立PVC的形态一致,但2种PVC的联律间期发生了明显改变,其改变幅度均≥70 ms,其中2例缩短,2例延长。1例孤立PVC时的联律间期亦不恒定。72例PVC触发的单形VT患者每天PVC次数为15 427±1 109,QT间期为404±15 ms,孤立PVC联律间期为419±22ms。4例PVC触发PVT/VF患者中3例1天的PVC次数与72例PVC触发的单形VT患者平均PVC次数相当。4例患者的QT间期及孤立PVC联律间期与另72例患者相当。而4例PVT/VF的周长均小于280 ms,明显短于72例VT的平均周长(324±59 ms)。72例单形VT患者发生晕厥比率4.1%;4例PVT/VF患者中发生晕厥者2例。采用激动标测和起搏标测证实4例患者PVC均起源于RVOT间隔侧,经射频导管消融PVC取得成功。结论起源于RVOT的PVC触发PVT/VF具有PVC联律间期不恒定及PVT/VF的周长短的临床特征,射频导管消融治疗有效。     

Empiric ablation of polymorphic ventricular tachycardia/fibrillation in the absence of a mappable trigger: Prospective feasibility and efficacy of pacemap matching to defibrillator electrograms

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Initial validation of a novel ECGI system for localization of premature ventricular contractions and ventricular tachycardia in structurally normal and abnormal hearts

Background

View into Ventricular Onset (VIVO) is a novel ECGI system that uses 3D body surface imaging, myocardial CT/MRI, and 12?lead ECG to localize earliest ventricular activation through analysis of simulated and clinical vector cardiograms.

On the mechanisms for the conversion of ventricular fibrillation to tachycardia by perfusion with ruthenium red

We have recently demonstrated that during pacing-induced sustained ventricular fibrillation (VF), perfusion of the heart with either ruthenium red (RR) or Ru 360, blockers of the mitochondrial Ca2+ uniporter, resulted in the reversible conversion of VF to ventricular tachycardia (VT). Here, we aimed at elucidating the electrophysiological mechanisms for the RR-induced conversion of VF to VT. The experiments were performed using Langendorff-perfused isolated rat hearts in which left ventricular pressure and left ventricular intracellular action potential were recorded. Perfusion with either RR or Ru 360 resulted in decreases in the action potential duration (APD), refractory period, and slope of APD restitution curves. These changes were antagonized by cotreatment with S(-)-Bay K8644. In addition, perfusion with verapamil produced the decreases in APD at 90% repolarization, refractory period and slope of APD restitution curves similar to the RR or Ru 360 perfusion. Such electrophysiological changes may be responsible for the reversible conversion of sustained VF to VT caused by perfusion with RR or Ru 360.     

急性心肌梗死患者急诊介入治疗中发生室性心动过速或心室颤动的预测因子和预后

目的评估急性ST段抬高性心肌梗死（STEMI）患者在导管室行急诊冠状动脉介入治疗（PCI）中室性心动过速或心室颤动（VT／VF）的发生率、预测因子和预后。方法调查了1136例症状发生后12h内行急诊PCI的急性STEMI患者，评估其VT／VF的发生率、预测因子和对患者住院期间及1年预后的影响。研究根据PCI术中发生VT／VF与否分为VT／VF组和无VT／VF组。结果1136例急性STEMI患者中在导管室PCI术中发生VT／VF62例（5．5％）。多元回归分析提示下列为发生VT／VF的预测因子：吸烟[相对危险度（OR）1．89，95％可信区间（CI）1．19-2．96]，缺乏应用β受体阻滞剂（OR2．54，95％ CI 1．45-4．27），从胸痛症状发生至入急诊室的时间〈180min（OR2．83，95％ CI 1．62-5．37），术前造影冠状动脉血流TIMI分级0级（OR2．44，95％ CI 1．45-3．89）和右冠状动脉作为梗死相关动脉（OR2．11，95％ CI 1．35-3．02）。随着危险因子的增加VT／VF的发生率也相应增加，从没有危险因子的0发生率到具有全部5个危险因子的14．0％发生率。VT／VF组与无VT／VF组患者住院期间和1年的预后相似（P〉0．05）。结论急性STEMI患者在导管室急诊PCI中VT／VF发生率低、治愈率高，对PCI成功率及住院期间和1年的临床结果无明显影响。本研究有助于发现存在发生VT／VF危险的患者，并强烈提示术前应用β受体阻滞剂可减少这些心律失常的发生。     

Ventricular tachycardia in myocardial infarction: Relation to heart rate and premature ventricular contractions

Analysis of monitored electrocardiograms, recorded in 77 patientsduring the first 48 hours following the onset of myocardialinfarction, revealed 492 episodes of ventricular tachycardiawith rates of 90–220 min^–1. Characteristics of theventricular tachycardia episodes were correlated with heartrate and with the rate and complexity of ventricular arrhythmiasin the 10-min period preceding ventricular tachycardia. Ventriculartachycardia with rates of 140–180 min^–1 and witha QS configuration was the most frequent event. The first ectopiccomplex of VT was R-on-Tin only 17.2%. Sinus tachycardia wasassociated with significantly fewer episodes of VT with ratesof 110–140min^–1 than when the sinus rate was normal.However episodes of ventricular tachycardia with rates of 181to 220 beats min^–1 were more frequent during sinus tachycardia.Analysis of the frequency of premature ventricular contractionsin the 10-min period immediately preceding ventricular tachycardiarevealed no premature ventricular contractions in 24.4% of cases.Multiple premature ventricular contractions with a frequencyof >5 min^-1 were observed in 8.4% of cases, multifocal in30.3%, couplets in 24% and early PVCs in 12.2%. In the minutebefore ventricular tachycardia, only 40.2% of cases displayedpremature ventricular contractions. In that minute, complexpremature ventricular contractions were distributed as follows:multifocal in 10%, couplets in 8.7% and early PVCs in 2.6% ofcases. Out of the total of 492 runs of ventricular tachycardia,5 cases (1%) resulted in ventricular fibrillation. The frequencyand complexity of premature ventricular contractions as wellas the characteristics of ventricular tachycardia were foundto be of little predictive value for the immediate developmentof ventricular fibrillation in patients with acute myocardialinfarction.     

Prevalence and prognosis of ventricular tachycardia/ventricular fibrillation in patients with post-infarction left ventricular aneurysm: Analysis of 575 cases

Background

We investigated the prevalence of ventricular tachycardia/ventricular fibrillation (VT/VF) in Post-infarction left ventricular aneurysm (PI-LVA) patients and analyze clinical outcomes in patients presenting with VT/VF.

扩张型心肌病QT离散度增加与室性心动过速及心室颤动关系

目的探讨扩张型心肌病患者QT离散度(QTinterval dispersion,QTd)增加与室性心动过速、心室颤动的关系。方法回顾性分析41例扩张型心肌病患者心电图QTd及JT间期离散度(JT interval dispersion,JTd)。结果扩张型心肌病患者QTd和JTd在伴室性心动过速和心室颤动者分别为(101±35)ms或(100±33)ms;而无室性心动过速或心室颤动者分别为(54±18)ms,(57±20)ms,差异有统计学意义(P<0.05,P<0.01)。结论QTd或JTd增加,室性心动过速、心室颤动发生的可能增大,表明QTd或JTd可作为早期预测室性心动过速和心室颤动的一个重要参考指标。