Lawrence Gilbert

Prediction of impending pacemaker failure in a pacemaker clinic

A pacemaker clinic has been established for the detection of impending pacemaker failure. Over a two year period, there were 121 operations on 87 patients, comprising a third of our living patients. Of the 93 pacemaker replacements evaluated, 77 (83 percent) were for failure of the pulse-forming circuit and 16 (17 percent) for wire dislogment, heart perforation on lead fracture. Sixty-four percent of the pacemakers were replaced electively as a result of changes detected in the electrical impulses or the electrocardiogram. Only 10 percent of replacements were elective in patients not attending the clinic. On the basis of observed defects in the pacemakers, a maximal yield of 83 percent elective pacemaker replacements could have been anticipated from the test procedures of the clinic. The most significant changes observed were decreases in the artifact amplitude and in rate, especially if found together or in conjunction with alteration in pulse width or impulse configuration. Absolute indications were uncommon but included rounding of the square wave of Electrodyne units and loss of synchronization of any unit with a sensing circuit (standby and synchronous pacemakers). A computer simplified the clinic procedure by providing real-time rapid analysis of the data and a neat, concise report for the records. However, the computer was not necessary for preparing and evaluating the tests although it will be used for analog to digital conversion in further development of the clinic. The clinic provides close follow-up of all patients and gives them and their physicians the assurance that trouble will usually be spotted before it occurs. We believe that premature and emergency replacement of pacemakers can be avoided with this semiquantitative method.

Permanent Pacemaker Insertion: A Five-Year Appraisal

uring the past five years, 115 permanent pacemakers have been implanted in 93 patients at the Newark Beth Israel Hospital. D An analysis of this experience has suggested what seem to be safe surgical techniques that can be used under a variety of circumstances. The choice of one method over another has become a complex matter because of the continuous development of new surgical techniques and new and improved equipment. This report will summarize the results of the past five years and will suggest what appears to be a sensible approach to surgical management of complete heart block and Stokes-Adams syndrome. The figures presented, it will be seen, are quite similar to those reported by others [2-4, 13-15].

CLINICAL USE OF A NEW TRANSVENOUS ELECTRODE

Recently we described a new type of transvenous electrode that displayed remarkably low thresholds for electrical stimulation of the heart and minimal polarization effects.I3 This electrode, called a differential current density (DCD) electrode, is constructed of a helical coil of platinum-iridium or Elgiloy, widened at its tip to form a cylinder with a surface area of more than 1 cm2. It is encapsulated in a silicone-rubber housing. The cylinder is opened at the very tip through the Silastic capsule where contact with the endocardium is made (FIGURE 1). When a current is applied, it passes through the hole at the tip so that the current density is low at the metal and high at the hole. The metal cyPnder is sufficiently large so that polarization effects are minimal at current densities needed for stimulation. At the same time, the effective area of the hole at the electrodemyocardial interface is so small that there is a high current density and therefore an extremely low excitation threshold. The concept of using a hole to increase current density was originally suggested by M a ~ r o . ~ Preliminary studies with various models of the DCD electrode in dogs revealed that excitation thresholds were ten to 20 times lower than those seen with standard metal electrodes. Moreover, it appeared that the transvenous model was sufficiently stable to warrant clinical trial.

Uncomplicated congenital mitral stenosis

Abstract 1. (1) A case of congenital mitral stenosis uncomplicated by other congenital defects is reported. 2. (2) The diagnosis and differential diagnosis of this condition are outlined. 3. (3) The possible causes and the pathology of the condition are presented. 4. (4) The problems of the surgical correction of this lesion are described and considered for future use.

A PLAN FOR THE TREATMENT OF COMPLETE HEART BLOCK AND STOKES-ADAMS SYNDROME WITH AN INTRACARDIAC DIPOLAR ELECTRODE AND A PERMANENT IMPLANTABLE PACEMAKER.

* From the Hemodynamics Department of the Newark Beth Israel Hospital, Newark, New Jersey. Presented at the annual meeting of the American College of Angiology, June 1962. t We use monitoring equipment manufactured by Electrodyne Company, Norwood, Massachusetts. Stokes-Adams syndrome can now be treated effectively by the permanent implantation of a transistorized electric pacemaker. Such a procedure requires a thoracotomy for the insertion of

A Decade of Nuclear Pacing

In April, 1973, a decade‐long study was begun on nuclear‐powered pacemakers. The first 15 of these were designed by the Numec Corporation under a contract from the United States Atomic Energy Commission. Altogether 151 units powered by the isotope Plutonium 238 were implanted in 131 patients; the pacemakers of 4 different manufacturers were used. The last nuclear pacemaker was implanted in January, 1983. The actuarial survival at 10 years was 92%, meeting the original performance goal of the Commission of 90%. Ninety pulse generators are still in service today; 25 patients have died and 36 pulse generators have been replaced with non‐nuclear units. The most common indication for replacement was an inappropriate pacing mode. This high reliability and superior performance suggest that continued use of a radioisotopic power source is justified, particularly if combined with the electronic circuits of todays dual‐chambered, multiprogrammable, and multifunctional pacemakers.

Choosing a vessel for aortocoronary bypass.

In practice, the surgeon is left with few choices of the proper ACB graft. His options are limited entirely to autologous tissues, of which the best is the great saphenous vein from the calf (Table 3). Actually, once leg veins and the internal mammary artery are no longer available there are few other choices worth considering. Small calibre allografts, however preserved, and synthetic grafts, are uniformly doomed to failure. The great saphenous vein from the calf is usually a single tube, of suitable diameter and strength for arterial replacement. Most of its tributaries lie in the upper third of the calf; this makes the lower segment preferable for the patient who requires only one or two bypasses. Variations in the normal anatomy have been illustrated.