1980s: EP and Pacing

The field of electrophysiology including electrocardiography, pacing, and invasive electrophysiology (EP) has been the subject of great interest since Henry Plummer had established an ECG laboratory at Mayo in 1914. The prelude to the 1980s included several years in the late 1970s during which experience in the field was accrued with both pacing and EP procedures (“HIS BUNDLE” recordings). Some of these focused on patients with SVT, specifically the Wolff-Parkinson-White syndrome (WPW), a condition that had been endlessly interesting, in part, because of the unusual ECGs and the tachycardia involved. There was robust growth of staff physicians and fellows coming from around the world who were extraordinarily productive in the field. Early publications tracked the Mayo pacing experience over two decades during which implantation moved from being a surgical specialty to being driven by cardiology operators in the Mayo catheterization laboratory. This two-decade experience also documented the rapid shift in pacing modalities as technology moved from single to dual chamber devices. Teaching, questioning, and problem-solving were eclectic and engaged. Favorite productive educational sessions were initiated, held every week at 5:00 pm in an establishment near the clinic campus which served liquid bread and popcorn. Out of these sessions came ideas for new studies, approaches, strategies of care, and intellectual property. Evaluation of the increasing number and complexity of pacing modes were the focus of study as well as early data on specific clinical circumstances such as the effect of MRI imaging on pacemaker function, the latter of which was studied in an animal model. Particularly noteworthy were studies on the hemodynamics of cardiac pacing including pacing-mediated tachycardia and the pacemaker syndrome. Of fundamental importance were the “HIS Books.” They were handwritten by the operators and included patient name, clinic number, indication for study, and diagnosis/diagnoses. These were the consecutive patient’s studies coming through the laboratory offering a wealth of information on indications for study and results, all tabulated into categories. They were used for manuscripts, presentations, and discussion. Looking at them now, the handwriting from the early physicians is readily identifiable; we can see who was doing what, well before the time of computerized records. The group was developing extensive experience with the WPW syndrome and what were called Kent bundles or now accessory AV nodal pathways. The earliest case in the operating room identified the specific location of the connection, transiently interrupted it, and stopped tachycardia. This set the stage for the extensive development of the surgical experience with patients with WPW which became a standard of care and then the migration to catheter ablation. Other surgical and catheter experiences included AVNRT from dual AV nodal pathways. Seminal studies included defining optimal strategies for infected pacemakers, the largest experience at that time of invasive assessment of syncope, and the effect of tilt table testing on rhythm disturbances. In an old GI room used for barium swallows, catheters could be placed in the supine position and tachycardia induced. Then the patient would be tipped upright to document the effects of position on the rhythm. That first example of this technology forms the basis for tilt table testing in use today. Other important observations included tachycardia-induced cardiomyopathy. The concept of inducing tachycardia with programmed electrical stimulation both SVT and VT was an essential part of the practice. This was used to evaluate symptoms, to test drugs for effectiveness, and to evaluate the possibility of implantable pacemakers that could be used to terminate tachycardia both SVT and VT. EP rounds in the CCU involved carrying a portable stimulator to identify if the medication the patient had received prevented re-induction of the tachycardia. Rounds were sometimes rather exciting both for the patient, the nursing staff, and the physicians involved. This use of electrical stimulation became a mainstay of the practice with its application perhaps for the first time in the field to ablate VT from the LV cavity using DC cardioversion.