Table of Contents
Significant Events in the 1980s:
- 1991: The Soviet Union is dissolved
- 1992: Aparthoid in South Africa ceases
- 1993: European Market begins
- 1997: Scottish researcher clones lamb
- 1999: First balloon flight around the world
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The Radioisotopic Pacemaker Experiment
By: Victor Parsonnet, M.D.
In the first days of pacing, a major problem was short battery life, with pulse generators lasting only 12 or 13 months. An exciting and reasonable alternate power source was a radioisotopic generator (RP). We were privileged to implant the first of these American-made devices in 1972. Within the next few years, we implanted 165 of them. The pacemaker had an expected life of 20 years. Availability of lithium-powered pacemakers with an expected life of about 10 years, and without the disadvantages of regulatory paperwork, eliminated the longevity advantage of RP's. The last RP was implanted in 1988. Actuarial survival curves illustrate that these devices performed as anticipated. Replacements, when needed, were for mode change, rather that battery failure. Pacemaker electronics have become so sophisticated that changing modes and parameters of pacing are easily done within the same implanted device. Use of a pacemaker with extended life expectancy should therefore be very cost-effective, since replacements for mode upgrades will not be needed. Therefore, consideration should be given once again toward utilization of radioisotopic energy source.
Parsonnet V. Bernstein AD, Perry GY.The nuclear pacemaker: Is renewed interest warranted. Am J Cardiol 1990; 66:837-842
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Schematic of a Sagittal Section Through the Left Ventricle (LV) Showing Pathways of Parasympathetic (Vagus) and Sympathetic Nerves
Most postganglionic sympathetic axons are located superficially in the periadventitia of coronary arteries.
Postganglionic parasympathetic axons cross the atrioventricular (A-V) groove in the subepicardium, but are located in the ventricular subendocardium. LAD = left anterior descending coronary artery; Cx = circumflex coronary artery.
(reproduced with permission from Zipes DP; Influence of myocardial ischemia and infarction on autonomic innervation of heart. Circulation 82:1096,1990.)
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Biatrial Synchronous Pacing:
Opening the Way to Cardiac Resynchronization Therapy
The ECG panel (leads I, II, and III) demonstrates the biatrial synchronous pacing.
During spontaneous sinus rhythm (left), the P wave duration is 160 ms indicating major intraatrial conduction delay with a typical morphology of complete Bachman's bundle branch block.
When the pacemaker is switched "ON" (↑), the early sinus activity is sensed by the high right atrial lead and immediately triggers biatrial pacing with full capture of the left atrium through the coronary sinus (CS) lead. Atrial resynchronization is demonstrated by a dramatic decrease in P-wave duration (100 ms).
The right ventricular (RV) lead is principally used for the needs of atrial resynchronization algorithms.
Daubert, JC. Eur. Heart J, 1991 Back to Top
The Relation Between Incidence and Total Number of Sudden Cardiac Arrest Deaths among Population Subgroups 
Approximation of incidence figures (percent per year) and the total number of events per year is shown for the overall adult population in the United States and for increasingly higher risk subgroups. The overall adult population has an estimated sudden death incidence of 0.1-0.2% per year, totaling more than 300,000 sudden deaths per year. Within subgroups identified by increasingly powerful risk factors, the incidence increases progressively, but is accomplished by a progressive decrease in the total number events, because of the progressively smaller denominator in the highest risk categories. This limits the impact of successful interventions identified for high-risk subgroups. Successful interventions among larger population segments will require specific markers to identify risk clusters of higher risk within the larger (lower risk) population groups.
From: Myerburg RJ. Kessler KM, Castellanos A: Sudden cardiac death: Structure, function and time-dependence of risk. Circulation (Suppi 1) 1992; 85:1-2 - 1-1<
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Transvenous Implantable Defibrillator. 
At the time of this work, ICDs required considerable expertise, multiple incisions, multiple long-length leads, long operative times, and higher surgical costs and were associated with significant morbidity and mortality.
The study by Bardy, et al, examined a left infraclavicular subcutaneous active can (or unipolar) defibrillation with a single standard-length RV electrode in cardiac arrest survivors. Testing occurred prior to implantation of standard nonthoracotomy defibrillation systems that were ultimately used in these patients.The unipolar system resulted in a defibrillation threshold of 9.3±6.0 J with 93% of patients requiring <20 J. Moreover, this system required only 3.4±0.8 VF inductions to measure the defibrillation threshold and 100±28 minutes to implement.
The unipolar defibrillation system proved as simple to insert as a pacemaker, required fewer VF inductions, demanded less technical expertise, and provided defibrillation at very low energy levels. It substantially reduced the mortality, morbidity, time, difficulty, and cost of defibrillator implantation while improving defibrillation efficacy. All defibrillators worldwide now use active can systems.
Reference: Bardy GH, Johnson G, Poole JE, Dolack GL, Kudenchuk PJ, Kelso D,Mitchell R, Hofer B:A simplified, single lead unipolar transvenous cardioverter-defibrillator. Circulation 88:543-547,1993.
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MADIT
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| Kaplan-Meier life-table cumulative-survival curves for the defibrillator and conventional-therapy groups in MADIT. |
In December 1990, the Multicenter Automatic Defibrillator Implantation Trial (MADIT) investigators initiated a prophylactic trial in which high-risk patients with coronary heart disease and asymptomatic non-sustained ventricular tachycardia were randomly assigned to an implantable cardioverter-defibrillator (ICD) or conventional medical therapy. MADIT, completed in March 1996 and published later the same year, demonstrated a significant (P=0.009) 54% reduction in all-cause mortality in ICD-treated patients when compared to non-ICD patients during an average follow-up 27 months for the 196 enrolled patients. This study, the first published randomized ICD trial, had a major impact on the use of ICD therapy in cardiology.
Moss AJ, Hall WJ, Cannom DS, et al. Improved survival with an implanted defibrillator in patients with coronary disease at high risk for ventricular arrhythmia. N EnglJ Med 1996;335:1933-1940
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Electrical Heterogeneity in the Heart 
Ventricular myocardium is comprised of at least three electrophysiologically distinct cell types: epicardial, endocardial and M cells. Because M cells display a longer action potential, transmural dispersion of repolarization exists under baseline conditions and is largely responsible for the electrocardiographic T wave. Amplification of this intrinsic heterogeneity by ion channel mutations or drugs that cause preferential prolongation of the M cell response, particularly in LV, leads to the development of the long QT syndrome and Torsade de Pointes. Exaggeration of transmural dispersion in RV, secondary to a marked abbrevation of the epicardial response, is believed to underlie VT/VF seen in the Brugada syndrome.
Antzelevitch C, Yan GX, Shimizu W, Burashbikov A: Electrical heterogeneity, the ECG, and cardiacarrhythmias., in Zipes DP, Jalife J (eds): Cardiac Electrophysiology: From Cell to Bedside, 3rd edition. Philadelphia, W.B. Saunders Co., 1999.
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Norman J. "Jeff" Holter - "Father" Of Ambulatory ECG Monitoring (1914 – 1983) 
Norman Holter realized that the newer trends in cardiologic practice would require ambulatory ECG documentation. The original 1947 unwieldy apparatus (Figure) consisting of a bulky ECG radio transmitter and heavy batteries (together weighing 85 lb) could not realistically be worn by a patient being monitored. By 1952 the cumbersome amplifier and transmitter had been refined from an 85 lb unit to a 2.6 lb amplifier and transmitter. One day, in the early 1950s, the renowned pioneer cardiologist of that era, Paul Dudley White, visited Holter in his laboratory in Helena, Montana. White was impressed and shortly thereafter with Dr White’s encouragement, Holter received some financial support from the National Institutes of Health. In 1962 Holter sent his brilliant senior engineer, William Glasscock, to work with Eliot Corday MD at the Cedars of Lebanon hospital in Los Angeles to demonstrate the handmade version of the Holter Monitor system which was the first clinical prototype. This led to the publication of the classic 1965 paper in JAMA “Detection of phantom arrhythmias and evanescent electrocardiographic abnormalities” by Corday et al. As a result of collaboration with Dr. Corday, Holter began his association with Bruce Del Mar (Del Mar Avionics) to manufacture the recorder.
Corday, E. JACC 1991;17:286-292
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