Michael D. Falkoff

Cephalic vein guide wire technique for implantation of permanent pacemakers.

This report describes a modified cephalic vein guide wire technique for the implantation of permanent pacemakers. The procedure was attempted in 11 patients only when pacing leads could not be passed directly into the exposed cephalic vein. Eight bipolar DDD (two leads), two unipolar DDD, and one bipolar VVI (one lead) pulse generators were implanted successfully, with only one relatively minor complication. The cephalic vein guide wire technique provides easy access to the subclavian vein and may allow implantation of most single- and dual-chamber pacemakers with only a cephalic vein cutdown.

Characterization of Pacemaker Arrhythmias Due to Normally Functioning AV Demand (DVI) Pulse Generators

Normally functioning DVI pulse generators with different electronic characteristics may cause complex cardiac arrhythmias that must not be interpreted as pacemaker malfunction. When there is no refractory period after the atrial output, a DVI pulse generator may deliver atrial pacemaker impulses at irregularly shortened intervals and produce an increase in the atrial pacemaker rate compared with the programmed free‐running AV sequential rate. Theoretically this variation of the atrial cycle length can occur only within a well‐defined range that represents the difference between the ventricular and atrial output escape intervals. In reality, the interplay of the spontaneous sinus rate, duration of AV conduction, time of sensing the ventricular electrogram in relation to the surface QRS complex, and the programmed AV sequential time all influence the atrial pacemaker rate. DVI pulse generators may also create interesting arrhythmias such as pseudopseudofusion beats (delivery of an atrial spike within the QRS complex), double pseudofusion beats, and double pacemaker impulses within the QRS complex according to the electrophysiologic circumstances and specifications of the pulse generator.

Hyperkalemia-induced failure of atrial capture during dual-chamber cardiac pacing

This report describes hyperkalemia-induced failure of atrial capture associated with preservation of ventricular pacing in a patient with a dual-chamber (DDD) pacemaker. This differential effect on atrial and ventricular excitability during cardiac pacing correlates with the well known clinical and experimental observation that the atrial myocardium is more sensitive to hyperkalemia than is the ventricular myocardium.

INTERATRIAL SEPTAL ANEURYSM, SYSTOLIC CLICK AND ATRIAL TACHYARRHYTHMIA- A NEW SYNDROME?

Abstract We are describing a case of atrial septal aneurysm (diagnosed by echocardiography), systolic click and atrial tachyarrhythmia. The implications of these findings are discussed.

Interpretation of Electrocardiograms Produced by a New Unipolar Multiprogrammable “Committed” AV Sequential Demand (DVI) Pulse Generator

This paper describes our approach to the interpretation of electrocardiograms produced by a new unipolar multiprogrammable “committed” DVI pulse generator (Intermedics) during normal function. The arrhythmias engendered by this new DVI pacemaker may be better understood by conceptualizing the recycling mechanism in terms of a simple atrial pulse generator with two important qualifica‐tions: (1) the ventricular stimulus obligatorily follows the atrial stimulus after 155 ms (AV sequential interval); (2) the pulse generator senses ventricular events (via the ventricular electrode) but recycles according to its atrial timing cycle (AA interval). These characteristics lead in turn to two important consequences: at the QA interval (from the onset of a sensed QRS complex to the succeeding atrial stimulus) must be longer than the VA interval (from a ventricular stimulus to the succeeding atrial stimulus) by a period equal to or slightly greater than the AV sequential time. This may be considered to represent a form of bysteresis, by the pacemaker refractory period always starts at the onset of an atrial cycle (AA interval) and therefore occurs after the delivery of an atrial stimulus or after a sensed ventricular event. The above characteristics may cause pacemaker stimuli to fall within the P wave, PR interval, QRS, ST segment and the ascending limb of the T wave during normal function of the pulse generator. Superficially, these peculiarities resemble malfunction and may be quite befuddling but they all occur predictably according to the electronic design of the pulse generator. (PACE, Vol. 4, November‐December, 1981)

The Noise Sampling Period: A New Cause of Apparent Sensing Malfunction of Demand Pacemakers

Two patients with Omni‐Stanicor®* pulse generators presented an apparent sensing problem characterized by intermittent reversion to fixed‐rate pacing only during atrial fibrillation with a very rapid ventricular rate, Every fixed‐rate cycle contained two unsensed beats. The first un‐sensed beat fell in the noise sampling period (the last 3/6 of the pacemaker refractory period) and, therefore, disabled the demand function of the pulse generator for a single timing cycle. The presence of two consecutively unsensed beats within one timing cycle (automatic or escape interval) during tachycardia suggests normal function of the noise sampling period of this particular pulse generator, rather than a true sensing problem. The diagnosis becomes evident if the sensing problem disappears when abbreviation of the refractory period occurs by reprogramming the pulse generator at a higher rate.

Magnet unresponsive pacemaker endless loop tachycardia

Endless loop tachycardia is a well-known complication of DDD pacing and is almost invariably terminated by conversion to the asynchronous DOO mode upon application of a magnet over the pulse generator. Occasionally magnet application is ineffectual because the ventriculoatrial (VA) synchrony of endless loop tachycardia is converted directly or indirectly to an atrioventricular (AV) desynchronization arrhythmia, another form of VA synchrony. This occurs when a paced ventricular beat engenders an unsensed retrograde P wave and the continual delivery of an ineffectual atrial stimulus during the atrial myocardial refractory period creates self-perpetuating VA synchrony. Upon magnet removal, AV desynchronization arrhythmia reverts immediately to endless loop tachycardia. In the absence of access to programmers, magnet unresponsive endless loop tachycardia can be easily and reliably terminated by chest wall stimulation through inhibition of the ventricular channel of the DDD pulse generator.

Pacemaker endless loop tachycardia: termination by simple techniques other than magnet application

PURPOSE Pacemaker endless loop (or reentrant) tachycardia (ELT) is often terminated by conversion to the asynchronous mode of pacing by simply placing a magnet over the implanted atrial tracking (DDD or VDD) pacemaker. We investigated three other simple methods of ELT termination--chest wall stimulation (CWS), provocation of myopotential oversensing, and chest thumping--that may be useful when the arrhythmia is unresponsive to magnet application or a magnet is unavailable. PATIENTS AND METHODS A modified CWS technique using an external pulse generator (pulse width = 40 msec) ordinarily used for transcutaneous cardiac pacing was tested in 74 patients (40 with unipolar and 34 with bipolar DDD devices). CWS inhibited the ventricular channel of all DDD pacemakers easily and reliably. CWS was then applied during ELT in 20 patients (10 with unipolar and 10 with bipolar DDD devices). Provocation of myopotential oversensing by the ventricular channel was attempted during ELT in 10 patients with unipolar DDD pacemakers. Chest thumping was tried during ELT in six patients. RESULTS CWS by the modified technique terminated ELT in all patients in whom the arrhythmia was induced. Myopotential oversensing resulted in successful ELT termination in six of the 10 patients. ELT was successfully terminated by chest thumping in four of six patients. CONCLUSION These simple techniques provide effective ways of ELT termination other than magnet application, and may be easily applied by physicians unfamiliar with the complexities of contemporary DDD pacemakers and their programmers.

Sources of Error in the Determination of Output Voltage of Pulse Generators by Pacemaker System Analyzers

The use of threshold or pacemaker system analyzers with widely different characteristics has introduced potential sources of error in the determination of the output voltage of pulse generators. This is further compounded by the availability of pulse generators with diverse waveform configurations and programmability capabilities. Because of this non‐uniformity, the physician must have some rudimentary knowledge of waveform characteristics and appreciate the limitations of threshold or pacemaker system analyzers to avoid the unnecessary replacement of normally‐functioning pulse generators.

Long-term management of ventricular tachycardia by implantable automatic burst tachycardia-terminating pacemakers.

This report describes the Jong‐term follow‐up of two patients who received implantable automatic burst tachycardia‐terminating ventricular pacemakers for the treatment of drug‐refractory sustained ventricular tachycardia. After implantation, both pulse generators continued to terminate ventricular tachycardia without any major complications. In one patient, after three years, many episodes of ventricular tachycardia were slower than the tachycardia‐detection criterion rate of 137 per minute; ventricular tachycardia was then terminated by chest wall stimulation that activated the burst function of the pacemaker. In this particular patient, the pulse generator was removed after four and one‐half years and replaced with a DDD system because of the pacemaker syndrome and attacks of ventricular tachycardia, often at a rate of about 100/minute. In the second patient, the pacemaker continued to terminate ventricular tachycardia for over five and one‐half years as determined by the repeated activation of the flag (memory) function of the pacemaker indicating detection of tachycardia by the pulse generator and resultant delivery of burst pacing.