Heart rate variability: standards of measurement, physiological interpretation and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology.

The National High Blood Pressure Education Program presents the complete Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Like its predecessors, the purpose is to provide an evidence-based approach to the prevention and management of hypertension. The key messages of this report are these: in those older than age 50, systolic blood pressure (BP) of greater than 140 mm Hg is a more important cardiovascular disease (CVD) risk factor than diastolic BP; beginning at 115/75 mm Hg, CVD risk doubles for each increment of 20/10 mm Hg; those who are normotensive at 55 years of age will have a 90% lifetime risk of developing hypertension; prehypertensive individuals (systolic BP 120-139 mm Hg or diastolic BP 80-89 mm Hg) require health-promoting lifestyle modifications to prevent the progressive rise in blood pressure and CVD; for uncomplicated hypertension, thiazide diuretic should be used in drug treatment for most, either alone or combined with drugs from other classes; this report delineates specific high-risk conditions that are compelling indications for the use of other antihypertensive drug classes (angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, beta-blockers, calcium channel blockers); two or more antihypertensive medications will be required to achieve goal BP (<140/90 mm Hg, or <130/80 mm Hg) for patients with diabetes and chronic kidney disease; for patients whose BP is more than 20 mm Hg above the systolic BP goal or more than 10 mm Hg above the diastolic BP goal, initiation of therapy using two agents, one of which usually will be a thiazide diuretic, should be considered; regardless of therapy or care, hypertension will be controlled only if patients are motivated to stay on their treatment plan. Positive experiences, trust in the clinician, and empathy improve patient motivation and satisfaction. This report serves as a guide, and the committee continues to recognize that the responsible physician's judgment remains paramount.

Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure

BACKGROUND Patients who survive life-threatening ventricular arrhythmias are at risk for recurrent arrhythmias. They can be treated with either an implantable cardioverter-defibrillator or antiarrhythmic drugs, but the relative efficacy of these two treatment strategies is unknown. METHODS To address this issue, we conducted a randomized comparison of these two treatment strategies in patients who had been resuscitated from near-fatal ventricular fibrillation or who had undergone cardioversion from sustained ventricular tachycardia. Patients with ventricular tachycardia also had either syncope or other serious cardiac symptoms, along with a left ventricular ejection fraction of 0.40 or less. One group of patients was treated with implantation of a cardioverter-defibrillator; the other received class III antiarrhythmic drugs, primarily amiodarone at empirically determined doses. Fifty-six clinical centers screened all patients who presented with ventricular tachycardia or ventricular fibrillation during a period of nearly four years. Of 1016 patients (45 percent of whom had ventricular fibrillation, and 55 percent ventricular tachycardia), 507 were randomly assigned to treatment with implantable cardioverter-defibrillators and 509 to antiarrhythmic-drug therapy. The primary end point was overall mortality. RESULTS Follow-up was complete for 1013 patients (99.7 percent). Overall survival was greater with the implantable defibrillator, with unadjusted estimates of 89.3 percent, as compared with 82.3 percent in the antiarrhythmic-drug group at one year, 81.6 percent versus 74.7 percent at two years, and 75.4 percent versus 64.1 percent at three years (P<0.02). The corresponding reductions in mortality (with 95 percent confidence limits) with the implantable defibrillator were 39+/-20 percent, 27+/-21 percent, and 31+/-21 percent CONCLUSIONS Among survivors of ventricular fibrillation or sustained ventricular tachycardia causing severe symptoms, the implantable cardioverter-defibrillator is superior to antiarrhythmic drugs for increasing overall survival.

A comparison of antiarrhythmic-drug therapy with implantable defibrillators in patients resuscitated from near-fatal ventricular arrhythmias

Healthy biological systems exhibit complex patterns of variability that can be described by mathematical chaos. Heart rate variability (HRV) consists of changes in the time intervals between consecutive heartbeats called interbeat intervals (IBIs). A healthy heart is not a metronome. The oscillations of a healthy heart are complex and constantly changing, which allow the cardiovascular system to rapidly adjust to sudden physical and psychological challenges to homeostasis. This article briefly reviews current perspectives on the mechanisms that generate 24 h, short-term (~5 min), and ultra-short-term (<5 min) HRV, the importance of HRV, and its implications for health and performance. The authors provide an overview of widely-used HRV time-domain, frequency-domain, and non-linear metrics. Time-domain indices quantify the amount of HRV observed during monitoring periods that may range from ~2 min to 24 h. Frequency-domain values calculate the absolute or relative amount of signal energy within component bands. Non-linear measurements quantify the unpredictability and complexity of a series of IBIs. The authors survey published normative values for clinical, healthy, and optimal performance populations. They stress the importance of measurement context, including recording period length, subject age, and sex, on baseline HRV values. They caution that 24 h, short-term, and ultra-short-term normative values are not interchangeable. They encourage professionals to supplement published norms with findings from their own specialized populations. Finally, the authors provide an overview of HRV assessment strategies for clinical and optimal performance interventions.

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An Overview of Heart Rate Variability Metrics and Norms.

Sudden cardiac death describes the unexpected natural death from a cardiac cause within a short time period, generally ≤ 1 h from the onset of symptoms, in a person without any prior condition that would appear fatal [1, 2]. Such a rapid death is often attributed to a cardiac arrhythmia, but with the advent of monitoring capabilities from implantable cardioverter-defibrillators (ICDs), it is now well recognized that classifications based on clinical circumstances can be misleading and often impossible, because 40% of sudden deaths can be unwitnessed [3]. Only an ECG or a ventricular electrogram recorded from an implanted device at the time of death can provide definitive information about an arrhythmia. Prodromal symptoms are often nonspecific, and even those taken to indicate ischemia (chest pain), a tachyarrhythmia (palpitations), or congestive heart failure symptoms (dyspnea) can only be considered suggestive. For these reasons, total mortality, rather than classifications of cardiac and arrhythmic mortality, should be used as primary objectives for many outcome studies.

Sudden Cardiac Death

https://www.annalsthoracicsurgery.org/article/0003-4975(92)91175-9/pdf

Subfascial implantation of implantable cardioverter defibrillator generator.

Ventricular tachycardia in plasma cell dyscrasia syndrome.

OBJECTIVE: To study the potential interactions in patients with endocardial permanent pacemakers and non-thoracotomy implantable cardioverter defibrillator (ICD) systems DESIGN: Case series and cohort study SETTING: Tertiary referral centre PATIENTS: Fifteen consecutive patients with both endocardial pacemakers (12 dual chamber and three single chamber) and non-thoracotomy ICD systems MAIN OUTCOME MEASURES: Detection inhibition of induced ventricular fibrillation; double counting; and pacemaker function after shocks In the evaluation of detection inhibition, 124 VF inductions were analysed for detection duration compared with induced VF episodes in controls with an ICD but without a pacemaker RESULTS: Two patients (13%) showed detection inhibition of VF and required pacemaker system change at the time of the ICD implant With the final lead position, despite frequent pacemaker undersensing of VF, ICD detection of VF was not inhibited during any induction, and neither initial detection nor redetection times for VF were different from controls Double/triple counting of pacemaker artefact and evoked electrogram was noted in three patients (20%) In two, this was remedied during the implantation procedure, and in the other it was abolished when amiodarone treatment was discontinued Pacemaker function was affected by ICD discharges in two patients, one who showed postshock atrial undersensing and loss of capture, and another whose pacemaker reverted to VVI mode CONCLUSIONS: When careful testing is performed at implantation to detect and remedy device interactions, non-thoracotomy ICD treatment and endocardial pacemakers can be used safely in combination

https://heart.bmj.com/content/heartjnl/78/1/50.full.pdf

Combined use of non-thoracotomy cardioverter defibrillators and endocardial pacemakers.

Massive hemotho-rax developed after placement of an implantable cardioverter defifarillator (JCD) in two patients who received postoperative anticoagulants. The possible relationship of (his complication to polyserositis after ICD implantation is discussed as are the possible adverse sequelae of early anticoagulation after ICD implantation.

Hemothorax associated with anticoagulation after placement of implantable cardioverter defibrillator: possible similarity to postinfarction Dressler's syndrome.

Forty patients (36 men and 4 women) with life-threatening arrhythmia received an implantable cardioverter defibrillator (ICD). Mean age was 63 years (range. 46 to 80 years). All patients had structural heart disease, with coronary artery disease in 32 patients, idiopathic cardiomyopathy in 7 patients, and hypertensive heart disease in 1 patient. Mean left ventricular ejection fraction was 29±13%. The clinical arrhythmia was out-of-hospital cardiac arrest in 14 patients (35%), symptomatic sustained ventricular tachycardia in 21 patients (53%), and episodes of syncope without documented spontaneous ventricular arrhythmia but ventricular tachycardia that was easily provoked at the time of electrophysiologic testing in 5 patients (13%). Sustained ventricular tachycardia was induced in 37 patients (93%) at basic electrophysiologic testing. The average number of drug failures was 2.9±1.4 per patient. One patient (2.5%) died perioperatively because of intractable ventricular tachycardia and ventricular fibrillation. During a median follow-up period of 5.5 months (range 2-21 months) 2 sudden deaths occurred. No patient had a serious complication during the follow-up period. Ten patients (25%) received antiarrhythmic drugs to suppress spontaneous ventricular tachycardia. Appropriate shock treatment was received by 18 patients (45%), and inappropriate shock treatment was received by 2 patients (5%). Several issues regarding use of the ICD must be considered, but the device seems to be useful, and it is associated with an accept-able rate of complications and good long-term success at the present time.

Ferdinand J. Venditti

Papers

Subfascial implantation of implantable cardioverter defibrillator generator.

Ventricular tachycardia in plasma cell dyscrasia syndrome.

Combined use of non-thoracotomy cardioverter defibrillators and endocardial pacemakers.

Hemothorax associated with anticoagulation after placement of implantable cardioverter defibrillator: possible similarity to postinfarction Dressler's syndrome.

Clinical experience in patients with implantable cardioverter defibrillators.