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Biomedical subjects

N Strathmore

Publications and source records attributed to N Strathmore.

5 recordsLinked to original sources

Electrical ablation of posteroseptal accessory pathways.

Electrical ablation of a posteroseptal accessory pathway by delivery of direct current electrical energy at the coronary sinus ostium was attempted in six patients. As a result of 12 procedures in these six patients, the posteroseptal accessory pathway was successfully ablated in one patient. Retrograde conduction only was affected in a further three patients, abolishing paroxysmal supraventricular tachycardia in two and reducing the tachycardia rate in one. One of the six patients developed coronary sinus perforation requiring prompt pericardial aspiration. The procedure is complicated, time consuming, of limited efficacy and coronary sinus perforation is a significant risk. Surgery remains the preferred option as a curative procedure for arrhythmias due to posteroseptal accessory pathway.

Adult

"Pacecare"--a computerized database for pacemaker follow-up.

A computerized database for pacemaker follow-up has been designed to run on IBM compatible hardware and to accept pulse generator and lead models of all manufacturers. Stored data includes patient, physician and implant details, indications for pacing, underlying rhythm, complications and management, program settings, and follow-up measurements. Typing is minimized by the use of "pop-up" lists and prepared pulse generator template displays. At each follow-up visit a patient's file is retrieved by surname or number, a visit record created, and measurements documented. As the template of the previous visit is used, recording of the clinic visit takes less than 1 minute. Changes in pacing rates (base or magnet), pulse widths, lead thresholds, lead impedance, and battery cell impedance can be displayed graphically for immediate recognition of end-of-life parameters or suspected malfunction. The program will print patient, implantation and clinic visit summary reports, clinic appointment lists, letters to patients, and annual reports. Two Melbourne hospitals have now entered over 3,600 patients into the database. Valuable information has been obtained regarding implantation details and trends with pulse generator and lead usage. Pacecare is a sophisticated, yet user friendly, computerized database for pacemaker follow-up. Recording of clinic visits is fast and changes in testing parameters can be recognized immediately.

Computer Systems

Rate responsive pacing using a minute ventilation sensor.

Minute ventilation, the product of respiratory rate and tidal volume, correlates directly with oxygen consumption, cardiac output, and heart rate. An implantable pacemaker has been developed which allows variation in pacing rate in response to measured changes in minute ventilation. This single chamber system measures transthoracic impedance between the tip electrode of a standard bipolar lead and the pulse generator case. Low amplitude current pulses (1 mA for 15 microseconds) are generated each 50 msec between the the ring electrode and the case. In the adaptive mode, the pulse generator calculates a rate response factor or slope after maximal exercise. This slope, which describes the relationship between pacing rate and minute ventilation together with the pacing rate limits are the only programmable rate responsive features. Minute ventilation rate responsive systems have been implanted in 12 patients (8 females, 4 males), of mean age 63 years. Indications were His bundle ablation (6), acquired complete heart block (4), and sick sinus syndrome (2). At post-implant exercise testing, pacing rate rose within the first minute. Peak rate and time to upper rate were dependent on workload. After exercise, pacing rate remained at peak for up to 2 minutes before a gradual fall to resting rate. Comparative studies of the minute ventilation and the activity sensor pacing systems in the same patients confirmed that the minute ventilation system more closely parallels normal sinus response to activity. The minute ventilation rate responsive pacing system is simple to programme, no special lead is required and the system is highly physiologic.

Aged