Heart Rate Dynamics and Vulnerability to Ventricular Tachyarrhythmias

Sudden arrhythmic death is the most common mode of death in Western countries. An increased understanding of the pathophysiology and trigger mechanisms of life-threatening ventricular tachyarrhythmias in patients with structural heart disease can provide a logical basis for improved therapeutic strategies in the prevention of sudden death. Analysis of heart rate variability (HRV) from ambulatory electrocadiographic recordings can identify the patients at increased risk for arrhythmic death after an acute myocardial infarction. Despite the epidemiological evidence of an association between low HRV and sudden arrhythmic death, the pathophysiological link of this association has not been completely understood. An important approach to understand this association is to investigate the heart rate dynamics before the spontaneous onset of life-threatening arrhythmias. Analysis of heart rate behaviour preceding the spontaneous onset of ventricular tachyarrhythmias has shown that overall HRV is impaired in patients who develop spontaneous ventricular tachycardia during the Holter recording. Recently, quantitative analysis of Poincare plots of successive R-R intervals has shown that reduced long-term R-R interval variability, associated with episodes of beat-to-beat sinus alternans, is a specific sign of a propensity for spontaneous onset of ventricular tachycardia. These studies suggest that abnormal heart rate behaviour reflects an electrical instability favoring the onset of life-threatening arrhythmia and provide evidence that altered neurohumoral or autonomic regulation is an important trigger mechanism for the spontaneous onset of life-threatening arrhythmia. Future research in larger patient populations will reveal whether analysis of dynamic behaviour of cardiac electrical signals will give new insights into the mechanisms of life-threatening arrhythmias and help in the development of new therapeutic options for the prevention of sudden arrhythmic death.     

Long-Term Outcome Following Programmed Electrical Stimulation in Patients with High-Grade Ventricular Ectopy

To determine if programmed electrical stimulation (PES) could be utilized to identify patients with high-grade ventricular ectopy at low- or high-risk for sudden cardiac death, we performed PES in 40 patients with high-grade ventricular ectopy refractory to conventional antiarrhythmic agents. Twenty-one patients had a previous myocardial infarction, five had cardiomyopathy, six had hypertension, three had valvular heart disease and five had no known structural heart disease. The mean age was 50 years (range, 18 to 76). During programmed ventricular stimulation, eight patients had inducible sustained (more than 30 seconds) monomorphic ventricular tachycardia (Group I) but in 32 patients sustained ventricular tachycardia was not inducible (Group II). None of the five patients without structural heart disease were inducible while seven out of 21 (33%) patients with previous myocardial infarction had inducible ventricular tachycardia (VT). Antiarrhythmic therapy was instituted in patients with inducible VT; patients without inducible VT did not receive antiarrhythmic agents. In Group I, seven of the eight patients are alive (mean follow-up, 16 months) and in Group II, 28 of the 32 patients are alive (mean follow-up, 17 months). None of the five deaths were sudden. We conclude that in the absence of antiarrhythmic therapy, the incidence of sudden cardiac death is very low in patients with high-grade ventricular ectopy who do not have inducible monomorphic ventricular tachycardia during programmed ventricular stimulation.     

Electrophysiological Evaluation of Sustained Ventricular Tachyarrhythmias in Idiopathic Dilated Cardiomyopathy

Sustained ventricular tachyarrhythmias and sudden death are particularly prevalent in patients with idiopathic dilated cardiomyopathy (IDC). In contrast to patients with ischemic heart disease, the value of electrophysiological stimulation (EPS) in patients with IDC has not yet been established. To clarify the role of EPS in these patients, we studied 19 patients (58 +/- 11 years) with IDC who had symptomatic ventricular tachycardia (VT) or ventricular fibrillation (VF). The mean left ventricular ejection fraction was 26 +/- 9%. Ten patients had survived out-of-hospital cardiac arrest, eight had documented sustained monomorphic VT and one patient had non-sustained VT associated with syncope. Thirteen of the 19 patients (68%) had their clinical ventricular tachyarrhythmias induced at EPS (12 VT, 1 VF). In nine of 13 patients (69%), the arrhythmias were subsequently suppressed during serial electrophysiological drug testing. During 17 +/- 11 months of follow-up, 10/19 (53%) patients experienced recurrence of their arrhythmias and nine out of 19 (47%) patients died; six died suddenly and three secondary to heart failure. There was no difference in arrhythmia recurrence between patients with and without inducible ventricular tachyarrhythmias at initial study. Furthermore, suppression of arrhythmia during serial testing did not predict outcome; recurrences were observed in five out of nine patients whose arrhythmias were suppressed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical Management of Patients with the Long QT Syndrome: Drugs, Devices, and Gene-Specific Therapy

The familial long QT syndrome (LQTS) is now recognized as a genetic cbannelopatby with a propensity to arrhythmogenic syncope and sudden death. Three genetic mutations have been identified that involve the slow and fast delayed potassium rectifier currents and the sodium current. Distinctive ECG T wave phenotypes are associated with each of the tbree genotypes. Current day therapy includes: β-adrenergic blocking drugs; pacemakers; left cervicothoracic sympathetic ganglionectomy; implanted cardioverter defibrillators; and possibly, drugs that improve mutant ionic cbannel dysfunction. LQTS bas provided unique insight into the complex relationsbip between ionic cbannel dysfunction and ventricular tacbyarrbytbmias.     

Combination Antiarrhythmic Drug Therapy For Ventricular Tachyarrhythmias

New antiarrhythmic drug regimens are constantly being sought because of the relatively low efficacy rates of standard antiarrhythmic agents in preventing induction of ventricular tachyarrhythmias; the application of these agents is also limited due to serious or debilitating side-effects. The combination of two antiarrhythmic agents with complimentary electrophysiologic activities and differing toxicities might offer significant advantages in overcoming the drawbacks of standard antiarrhythmic drug therapy. A knowledge of the pharmacodynamics of the major classes of antiarrhythmic agents will allow informed choices of drugs for use in combination therapy. Judging antiarrhythmic drug efficacy is a complex problem, requiring an understanding of the influence of the arrhythmia monitoring technique, arrhythmia morphology and the response to previous drugs on drug efficacy rates, so that accurate comparisons of drug effectiveness can be made among different agents or combinations. A number of combination therapies have been tested for suppression of complex ventricular ectopy, nonsustained ventricular tachycardia and sustained ventricular tachycardia and ventricular fibrillation. The most successful combinations have been those using class IA and IB agents and class IA and II agents. In general, these combinations tend to show higher efficacy rates in suppressing all forms of ventricular ectopy and ventricular tachyarrhythmias, and usually have a lower incidence of toxic side-effects compared with individual agents alone. On the basis of these initial results, it seems warranted to perform further studies to explore these combinations in larger populations and to test new combinations developed on the basis of pharmacodynamic principles.     

Tachyarrhythmias and catheter ablation in adult congenital heart disease

Advances in surgical technique have had an immense impact on longevity and quality of life in patients with congenital heart disease. However, an inevitable consequence of these surgical successes is the creation of a unique patient population whose anatomy, surgical history and haemodynamics result in the development of a challenging and complex arrhythmia substrate. Furthermore, this patient group remains susceptible to the arrhythmias seen in the general adult population. It is through a thorough appreciation of the cardiac structural defect, the surgical corrective approach, and haemodynamic impact that the most effective arrhythmia care can be delivered. Catheter ablation techniques offer a highly effective management option but require a meticulous attention to the real-time integration of anatomical and electrophysiological information to identify and eliminate the culprit arrhythmia substrate. This review describes the current approach to the interventional management of patients with tachyarrhythmias in the context of congenital heart disease.     

原发性高血压非药物治疗的评价

原发性高血压是一种危害人类健康的重要疾病，改变生活方式有助于疾病的治疗。文章应用循证医学方法，评价了近期大型随机对照试验中生活方式改变对血压的影响。研究发现，低钠饮食、控制体重、体育锻炼不仅有助于血压控制，且具有良好的卫生经济学价值。     

Empiric Amiodarone versus "Ineffective" Drug Therapy in Patients with Refractory Ventricular Tachyarrhythmias

Because of its presumed unique efficacy, amiodarone (AM) is often used to treat patients whose sustained ventricular tachyarrhythmias (VT/VF) appear to be drug-refractory. To examine the efficacy of AM in such patients, we performed a retrospective analysis of 77 patients with drug-refractory VT/VF treated with either empiric AM or with drugs predicted during electrophysiological (EP) testing to be ineffective (ID). To qualify for the study, patients had to have spontaneous, symptomatic VT/VF, and persistently inducible VT during serial EP testing with drugs. All 77 patients were offered therapy with AM. Those who refused were treated with ID, whenever possible, an ID was selected which "improved" the EP study compared to baseline. Originally, 68 patients elected AM and nine elected ID. Because of drug intolerance or inefficacy, 10 patients crossed over during the course of the study; a total of 71 patients were followed on AM for 15.7 +/- 11.0 months, and 16 on ID for 17.8 +/- 10.8 months (mean +/- SD). During follow-up, the cumulative recurrence of VT/VF at 6, 12, and 24 months for AM versus ID was 16 +/- 5% versus 44 + 12% (P less than 0.002), 32 +/- 6% versus 44 +/- 12% (NS), and 41 +/- 7% versus 44 +/- 12% (NS) (+/- SE). The recurrence of VT was significantly lower in the AM group only for the first 6 months of therapy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ventricular Fibrillation Survivors in whom Tachyarrhythmia Cannot Be Induced: Outcome Related to Selected Therapy

Eight-five patients were studied to determine the prognosis of the ventricular tachyarrhythmias at the time of electrophysiologic study. Twenty-five patients (29%) were not inducible when we used a stimulation protocol consisting of up to four extrastimuli delivered at two right ventricular sites. Patients with no inducible arrhythmias were younger (53 vs 59 yrs; p = .06) and had higher ejection fractions (.49 vs .34; p less than .04) than the inducible ventricular fibrillation survivors. Sex, cardiac diagnosis, time from event to electrophysiologic study, and antiarrhythmic therapy at the time of event did not discriminate between those with and those without inducible ventricular tachyarrhythmias. Survival free of recurrent sudden death or ventricular tachycardia was .86 +/- .05 and .95 +/- .05 for patients with and without inducible tachyarrhythmias, respectively (p = .22). Nine of 25 (36%) patients with no inducible arrhythmias developed inducible ventricular tachyarrhythmias when testing was repeated with an antiarrhythmic drug. Ventricular fibrillation survivors not inducible at the time of programmed ventricular stimulation (using a stimulation protocol consisting of four extrastimuli delivered at two right ventricular sites) seem to have a good prognosis. Many "noninducible" patients develop inducible tachyarrhythmias when placed on antiarrhythmic therapy. Because it is possible that these drugs are proarrhythmic, empiric antiarrhythmic therapy should be avoided in these patients.     

Nonpharmacological approaches in the management of hypertension

Purpose: The purpose of this article is to discuss the holistic evaluation of the hypertensive patient and review evidence-based nonpharmacological treatments to help patients achieve maximum therapeutic benefits with minimal side effects.
Data sources: Health sciences literature was reviewed using the following databases: Medline, PubMed, and Cumulative Index to Nursing and Allied Health Literature.
Conclusions: Hypertension remains a major public health problem, affecting 65 million Americans and contributing to excess morbidity, mortality, and indirect and direct healthcare costs. Improving clinical outcomes will reduce human suffering as well as the economic burden associated with this disease. Nonpharmacological strategies are recommended as successful primary and adjunctive treatment options for lowering blood pressure. Moreover, the benefits of many of these approaches extend to and promote overall health and well-being.
Implications for practice: Nurse practitioners who incorporate nonpharmacological options in the management of hypertension can improve clinical outcomes.     

Predictors of Device Activation for Ventricular Arrhythmias and Survival in Patients with Implantable Pacemakers/Defibrillators

Predictors of survival and arrhythmia recurrence for patients with implanted defibrillators have been reported but patients with sustained, well-tolerated ventricular tachycardia were often excluded from these trials. Arrhythmia recurrence and survival in populations including these patients have been less well studied. The purpose of the present study was to examine predictors of spontaneous ventricular arrhythmias and mortality in patients who received a tiered therapy antitachycardia pacemaker/defibrillator for ventricular tachycardia, fibrillation, or both. Three hundred thirty-seven patients who received a Ventritex CADENCE® tiered therapy antitachycardia device at one of 19 participating centers between July 11, 1989 and March 4, 1991 are included in this retrospective analysis. Diagnostic summary data and stored electrograms telemetered from the implanted device were assessed to determine characteristics of recurrent arrhythmias. Mean follow-up was 360 ± 10 (SEM) days. Thirty-three patients died during follow-up. At least one recurrent ventricular arrhythmia was observed in 205 patients (61 %). A total of 7,539 episodes were observed with a mean of 37 ± 5 per patient. Patients with recurrent ventricular arrhythmias were slightly but significantly older (64 ± 0.7 vs 59 ± 1.2 years; P < 0.001) but were not distinguished by gender or underlying structural disease. Patients whose presenting arrhythmia was monomorphic ventricular tachycardia were more likely to experience recurrent ventricular arrhythmias (69% recurrence rate) than patients presenting with ventricular fibrillation or polymorphic ventricular tachycardia (46% recurrence rate; P < 0.001). Cycle length of spontaneous tachycardia was also a predictor of arrhythmia recurrence. Patients having slower ventricular arrhythmias were less likely to remain recurrence free. Mean left ventricular ejection fraction was similar for patients with and without recurrences. Younger age and absence of arrhythmia recurrence but not presenting arrhythmia were predictors of survival. We conclude that age and presentation with monomorphic ventricular tachycardia are important predictors of arrhythmia recurrence for this patient population. Exclusion of patients with monomorphic ventricular tachycardia underestimates the rate of recurrent ventricular arrhythmias and utilization of device therapy.     

Ventricular Tachycardia Surgery in 1992: Did the Automatic Defibrillator Change This Approach?

The role of ventricular tachycardia (VT) surgery has been changed since the automatic implantable cardioverter defibrillator (ICD) is available. We studied the follow-up of 131 patients who underwent mapping guided surgery due to recurrent VT refractory to antiarrhythmic drug treatment. There were 65 patients operated upon between 1980–1985 (group I) and 66 patients between 1986–1991 (group II). Ten patients (8%) died perioperatively (< 3 weeks after surgery) [7/65 patients, 11%, in group I and 3/66 patients, 5%, in group II (P = 0.15)]. During a mean follow-up of 41 ± 24 months, 38 of 121 patients died (31%), significantly more patients in group I (24/58 patients, 41%) than in group II (14/63 patients, 22%) (P < 0.05). In group I, there was a higher incidence of sudden (7/58 patients, 12%) or cardiac death (15/58 patients, 26%) than in group II (sudden death 4/63 patients, 6%, cardiac death 7/63 patients, 11%) (P < 0.05). There was a similar incidence of VT recurrences between group I(9/65 patients, 14%) and group II (9/66 patients, 14%). Our data show that the indication for VT surgery has changed since the ICD is available because of better patient selection.     

Future Directions: Electrical Therapy for Cardiac Tachyarrhythmias

Directions and research opportunities in basic animal and clinical investigations and in industry that relate to the application and development of electrical devices which control tachyarrhythmias are presented. In basic research, a better understanding of mechanisms responsible for tachyarrhythmias, their onset and methods of termination, would provide increased rationale for selecting a particular therapeutic approach. Knowing the distribution in the heart of applied electrical current when delivered by different types of electrodes placed at different myocardial sites would be helpful. Clinically, we must develop appropriate algorithms to accurately differentiate sinus tachycardia, the various forms of supraventricular tachycardias and ventricular tachycardia. These must be incorporated into future cardioverters and defibrillators. In industry, new sensors, electrodes, expanded telemetry capabilities and implanted microprocessors will aid in creation of a universally applicable generic form of electrical therapy that can be programmed to treat any form of tachycardia.     

Causes of Death in Patients with Unipolar Single Chamber Ventricular Pacing: Prevalence and Circumstances in Dependence on Arrhythmias Leading to Pacemaker Implantation

Cardiac pacing improves the prognosis of patients with severe impulse formation and conduction disturbance, though sudden death can occur frequently in paced patients. In the present study, we analyzed the causes and the circumstances of 378 deaths in 2,243 paced patients followed over a 5-year period. Sudden cardiac death occurred in 71 of these 378 patients (18.7%), 56 patients died of stroke (15%), heart failure was the cause of death in 91 subjects (24%). We analyzed the causes of death in two groups with respect to the arrhythmia that had led to pacemaker implantation. The prevalence of cardiac sudden death was higher in patients with AV block than in patients with sick sinus syndrome, while stroke was more frequent in patients with sick sinus syndrome, particularly those with both fast and slow components. Atrial fibrillation is common in patients with sick sinus syndrome and is an important well-known risk factor for stroke. Death from heart failure was frequently reported in our population, but in our study group only a few patients had heart failure at the moment of pacemaker implantation. We conclude that sudden death is a common event in paced patients and the disturbance that led the patient to pacemaker implantation was also a factor in the cause of death.     

The ESVEM Trial: Impact on Treatment of Ventricular Tachyarrhythmias

The ESVEM (Electrophysiologic Study Versus Electrocardiographic Monitoring) trial was a prospective, randomized study, initiated in 1983, to compare the outcome of patients in whom antiarrhythmic therapy was guided by serial electrophysiological study with the outcome of patients in whom therapy was guided hy electrocardiographic monitoring. In a surprising finding, there was no difference in rates of arrhythmia recurrence or mortality between the two methods. Subsequent reanalyses using more stringent criteria for both methods or a combined assessment have not significantly improved the predictive accuracy of guided therapy. Because drug therapy in each limh was also randomized, a comparison of specific antiarrhythmic agents was also possible: sotalol therapy and the absence of previous antiarrhythmic drug therapy were associated with a reduction in arrhythmia recurrence. Survey data suggest that the results of this trial have influenced clinical practice.     

Value of Heart Rate Variability Parameters for Prediction of Serious Arrhythmic Events in Patients with Malignant Ventricular Arrhythmias

Heart rate variability (HRV) assesses the electrical stability of the heart and can identify patients at risk of sudden cardiac death (SCD). The value of 10 HRV parameters from 24 hour ECG (in both time and frequency domain) to predict serious arrhythmic events (SAE) in a group of 56 patients with ventricular tachycardia and/or ventricular fibrillation of different etiologies not due to acute myocardial infarction was explored. Eighteen patients had low left ventricular ejection fractions (LVEF). During follow-up (6–46 months, mean = 24) 8 SCD and 12 recurrences of malignant ventricular arrhythmias or ICD discharges were recorded. Proportional hazard analysis (Cox model) for SAE revealed that the mean of all 5 minute standard deviation of RR intervals (SD) and the amplitude of low frequency spectrum (L) were independent risk factors of SAE (P < 0.05). The best models were: SD+EF and L+EF where predictive values were high (sensitivity approximately 60%, specificity over 95%, positive predictive value over 90% and negative predictive value approximately 80%). Event-free survival curves revealed a significantly shorter survival in patients with EF < 40%: 47% vs. 92%, SD < 43 ms; 56% vs. 92% and L < 16 ms; 56% vs. 89% (all P < 0.001) after 2 years. The subgroup with low EF and SD < 43 ms revealed a significantly shortened survival (27% vs 83% at 2 years, P < 0.01). Some HRV parameters, SD from the time and L from the frequency domain, were predictive of a fatal outcome in VT/VF patients. Combined SD +EF and L +EF values are powerful predictors of serious arrhythmic events.