How to program rate responsive pacemakers.

Because oxygen uptake (VO2) increases linearly with heart rate during exercise, the oxygen pulse reserve (OPR) method (VO2 reserve divided by heart rate reserve) may provide a valid guide for rate responsive parameter tailoring. Using custom-made software (Pacing Rate Profile Software [PRPS]) it is possible to predict the exercise pacing rate profile with significant accuracy, according to the patient's functional class when ergospirometry apparatus is not available for a cardiopulmonary stress test (CPX). PRPS for Windows is based on the OPR method and some known workload/metabolic cost of exercise relationships during effort. The present study had two aims; first, to evaluate the reliability of PRPS in accurately predicting pacing rate profiles; and second, the suitability of activity and metabolic rate responsive sensors in supplying pacing rates sufficiently near to those predicted using CPX or PRPS. To test the reliability of PRPS we studied 244 patients, NYHA Class I-II, under two different stress test protocols. In one, the bicycle protocol (25 W, 2-minute steps), we tested 137 normal patients (94 men and 43 women, mean age 67 +/- 15 years). Sixty-eight of these were simultaneously CPX tested. PRPS predicted pacing rates were matched against the patients' sinus rhythms or their theoretical CPX measured VO2 heart rates (OPR method). Linear regression analysis was highly significant (r = 0.93 and r = 0.97, respectively). The other, the treadmill protocol, consisted of three different protocols. (1) Speed Incremental Treadmill Stress Test (SITST): 57 patients underwent CPX (33 men and 24 women, mean age 67 +/- 15 years, NYHA Class I-II). All had been pacemaker implanted for SSS and/or advanced atrioventricular block (AVB). PRPS pacing rates were matched against CPX VO2 OPR calculated heart rates (r = 0.93), (linear regression analysis). (2) CAEP: 30 patients underwent CPX (26 men and 4 women, mean age 61 +/- 11 years, NYHA Class I-II). Thirteen of them had been pacemaker implanted for SSS and/or advanced AVB. In all 30 patients the PRPS rates were matched against CPX VO2 calculated rates (r = 0.90). In the 17 normal nonimplanted patients, the PRPS rates were also matched against sinus rhythms, (r = 0.80). (3) Weber: 20 patients underwent CPX (16 men and 4 women, mean age 68 +/- 8 years, NYHA Class I-II). As above, in six normal nonimplanted patients, statistical analysis between PRPS rates and sinus rhythms was performed (r = 0.89). The comparison between PRPS theoretical pacing rates and VO2 predicted rates in all 20 patients was also statistically significant (r = 0.93). Finally, to test the reliability of PRPS also in NYHA Class III-IV patients, we tested 22 implanted patients (15 men and 7 women, mean age 70 +/- 9 years) and compared PRPS predicted rates against VO2 CPX measured rates (r = 0.92). To determine if the wide variety of RR pacers were able to supply pacing rates near to those predicted, whether by means of CPX or PRPS, we studied a total of 89 patients: 49 of these (26 men and 23 women, mean age 66 +/- 12 years) had been implanted with activity sensors; 12 patients (11 men and one woman, mean age 70 +/- 7 years) had been implanted with metabolic sensors, and finally 28 patients (19 men and 9 women, mean age 70 +/- 12 years) had been implanted with dual sensors (activity + QT or minute ventilation). Linear regression analysis showed r = 0.93 for activity sensors, r = 0.94 for metabolic sensors, and r = 0.92 for dual sensor. In conclusion, when rate responsive pacing causes symptoms or functional impairment, physicians must provide a personalized rate response tailoring derived from precise, simple physiological testing. OPR is an easy physiological method for tailoring rate response settings, suitable for activity and metabolic sensors. When ergospirometry apparatus is not available, PRPS can successfully replace CPX testing for tailoring.

Cardiac rehabilitation in patients with rate responsive pacemakers.

This study investigated the suitability of our oxygen pulse reserve (OPR) method for tailoring parameters of rate responsive pacemakers and planning aerobic rehabilitation programs. We selected 11 patients, NYHA Classes I-III (7 males and 4 females; mean age 60 years, range 18-83), with rate responsive pacemakers implanted for high degree AV block and chronotropic incompetence. Five pacemakers had activity sensors, 4 had temperature sensors, and 2 had dual sensors. All patients underwent a cardiopulmonary stress test (CPX). We determined anaerobic threshold time (ATT), VO2/AT, total exercise time (TET), VO2 Max, and VO2 AT/VO2 Max. OPR (mL-O2/beat) was calculated for each patient using the formula OPR = (VO2 Max - VO2 resting)/(HR Max - HR resting). During CPX, this slope was used as the rate response tailoring guideline by comparing the mL-O2/beat equation and the pacing rate. Rate response settings were modified until the optimal relationship between theoretical and paced rate was obtained. The work protocol yielded rate response settings capable of providing pacing rates within +/- 10 beats of the theoretical values. Data relating to theoretical and measured rates have been analyzed statistically. Patients underwent an aerobic rehabilitation program that followed the American College of Sports Medicine guidelines. Pacing rate at the anaerobic threshold was considered the border for an aerobic workload. After 2-7 months, all patients showed an evident improvement in ATT (92%), VO2/AT (48%), TET (49%), VO2 Max (23%), and VO2 AT/VO2 (21%). Particularly, two patients improved from Weber Class C to A, and three improved from C to B. At each CPX step, the mean values of pacing rate and theoretical rate almost overlap, and the relevant coefficients suggest an excellent correlation (P < 0.001). Our OPR method for tailoring rate response provides the basis for an effective rehabilitation program with functional advantages for patients.

[Use of esophageal atrial electrogram and an external Thera VDD pacemaker in atrial-triggered ventricular pacing in acute myocardial infarction complicated by total AV block and low cardiac output]. / Uso dell'atriogramma esofageo e di un pacemaker Thera VDD esterno per un paging ventricolare atrioguidato in corso di infarto miocardico acuto complicato da blocco AV totale e bassa portata cardiaca.

Aim of this short report is to present a simple and fast technique to pace in VDD mode patients with acute myocardial infarction associated with third degree AV block and haemodynamic deterioration. VDD pacing was obtained using atrial electrogram recorded by trans-oesophageal catheter and a Medtronic Thera VDD pace-maker as temporary pace-maker.

A new acceleration driven pacemaker: rate modulation versus normal sinus rhythm--comparison during treadmill exercise.

The pacing rate response of a new acceleration driven pulse generator (SWING 100, SORIN BIOMEDICA) was compared with simultaneous normal sinus rhythm (NSR) during two different treadmill exercises. This pacemaker has a gravitational acceleration sensor able to discriminate between physical activities and vibrations. Six healthy volunteers (three male, three female; aged 21.7 +/- 4.3 years), with the pacemaker strapped to their right infraclavicular area, performed each test three times with different rise response curve (RRC) each time: fast, normal, and slow. The fall response curve used was the same as the rising one during each test. Pacing rates were recorded using the VEGA analyzer (SORIN BIOMEDICA) and compared with simultaneous NSR recorded by a 7-channel ECG recorder (MINGOGRAF 7, SIEMENS). During all tests immediate (within seconds) rapid increase in pacemaker rate was seen up to about 60 seconds, then a slower increase followed thereafter. The mean correlation between pacing rates and NSR during the Bruce tests were 0.7941 +/- 0.10, 0.8562 +/- 0.14, and 0.8292 +/- 0.07; during the discontinuous tests 0.7292 +/- 0.16, 0.7233 +/- 0.10, and 0.7480 +/- 0.11 for fast, normal, and slow RRC, respectively. Each 30 seconds, nonsignificant differences were present between pacing rate and NSR during all the discontinuous tests; similar responses were observed only during the first two stages of Bruce tests after which NSR was significantly higher than pacemaker rates. The speed of rise to upper rate was the main difference between the different programs (fast, normal, and slow). The discontinuous tests showed that the pacemaker responds more to speed than to grade.(ABSTRACT TRUNCATED AT 250 WORDS)

[Ventricular stimulation triggered by esophageal atriogram: a new technique of temporary physiologic stimulation in the course of acute myocardial infarct complicated by atrioventricular block and low cardiac output]. / Stimolazione ventricolare triggerata dall'atriogramma esofageo: nuova tecnica di stimolazione temporanea fisiologica in corso di ima complicato da bav avanzato e bassa portata cardiaca.

Advanced atrio-ventricular (AV) block during acute myocardial infarction (AMI) is considered a complicating dysrhythmia as the well as mechanism responsible for occurrence of life-threatening hemodynamic changes. Often, simple VVI pacing can result insufficient in improving the decreased cardiac output. VDD pacing, which preserves atrial contribution, should represent the most effective electrical approach; therefore, it requires intracavitary placement of 2 catheters. In 10 pts (6M, 4F, mean age of 63.8 +/- 6.6 years) with advanced AV block due to AMI (4 inferior, 6 anterior) and without sinus node dysfunction, we performed stable VDD stimulation (mean 16.6 +/- 20.6 hours) using only one catheter positioned in the right ventricle while the atrial impulse, filtered (50-70 Hz) and amplified through a special device, was derived from the esophagus. Such technique is rapid and reliable, avoiding problems associated with atrial sensing and catheterization.

[Malignant ventricular hyperkinetic arrhythmia: role of permanent electric treatment]. / Aritmie ipercinetiche ventricolari maligne: ruolo del trattamento elettrico definitivo.

While the technics of cardiac pacing have shown to have a precise role in the diagnosis and treatment of ventricular arrhythmias on a temporary basis, the role of permanent antiarrhythmic devices (PAD) in the treatment of these arrhythmias is still ill defined mainly because of the technological limits concerning the pacemakers and the frequent complications observed during the attempts to interrupt such tachycardias. On the basis of the available data and of theoretical considerations, three groups of pts susceptible of treatment with PAD can be selected: a) pts with brady-dependent arrhythmias where PAD is used as a prophylactic mean; b) pts with recurrent sustained ventricular tachycardia refractory to medical treatment, in whom PAD can be used to interrupt tachycardia; c) pts affected by ventricular fibrillation or rapidly deteriorating ventricular tachycardia (sudden death pts), refractory to conventional treatment, in whom the implantable defibrillator represents the only therapeutic possibility. Even if scanty, the data available seem to confirm that PAD does have a role in the treatment of malignant arrhythmias, although in selected cases and almost always together with drug treatment.

[The permanent electrostimulation with ventricular programmable pacemaker (author's transl)]. / L'elettrostimolazione definitiva con pacemaker ventricolare programmabile.

The purpose of this study is to evaluate the directions, reliability and long-term results of ventricular programmable pacemakers (PPM's). One hundred and ten PPM's, types Cordis and Medtronic, were implanted in 60 patients (pts) with intermittent or paroxysmal 2 degrees, 3 degrees a-v block and in 50 pts with S.S.S., mostly symptomatics, with a follow-up of 45 months. We did not observe either spontaneous or wrong reprogrammations nor circuit failure. In 92% of pts with Omni-Stanicor Cordis PM's, the stimulation was effective at the "lower" current amplitude, hence a longer life of the generator. Eighteen pts (16.3%) needed to raise ventricular rate (average 65 bpm): 6 pts for dizziness, syncopes or cardiac failure; 2 pts to control ventricular arrhythmias; 10 pts for a stable bradycardia lower than 50 bpm. In 11 pts with bradyarrhythmia due to S.S.S., cardiac output (CO) was measured both with thermodilution and echocardiography ("mitral valve echogram", being "r" of the two methods = 0.92), in spontaneous rhythm (63.3 +/- 3.13 bpm) and increasing artificially heart rate to 74.8 +/- 3.0 bpm; CO decreased from 4.65 +/- 0.13 l/min to 3.58 +/- 0.09 l/min, likely for the loss of atrial pumping. Similar results were obtained in other pts evaluated only with echocardiographic method after PM implantation: some of these underwent a further echocardiographic haemodynamic evaluation after 15 days of constant ventricular pacing at a mean rate of 75 bpm, with a different behaviour among them. This emphasizes the utility of PPM's in preserving spontaneous rhythm until bradycardia reaches dangerous levels and also the usefulness of echocardiography to evaluate, haemodinamically, the paced patient's ventricular performance.

[Clinical and electrophysiological indications for permanent electrostimulation in sick sinus syndrome (author's transl)]. / Indicazioni cliniche ed elettrofisiologiche alla elettrostimolazione definitiva nella malattia del nodo del seno.

In 49 patients with sick sinus syndrome the following electrophysiological parameters were studied: sinus node recovery time and conduction time, atrial and AV nodal refractory periods, atrioventricular and intraventricular conduction. Moreover, pharmacological, vagal and sympathicomimetic stimulation were performed. These data were related to the clinical picture to establish any possible correlation leading to a more specific therapeutical choice. Patients were divided in two groups: group 1, with a prevalence of tachyarrhythmic symptoms and a lesser incidence of syncope, in which cases the sinus node function appeared to be only slightly affected. In group 2 small incidence of tachyarrhythmias and a clear prevalence of syncope with severe impairment of sinusal automaticity and/or sinoatrial conduction were present; AV and IV conduction disturbances were equally distributed in both groups. In more than 1/3 of the cases of the group I arrhythmias were succesfully treated with pharmacological therapy only, with Group 1 A antiarrhythmic agents in most cases. In the other cases of this Group and in all cases of Group II permanent electrical stimulation alone or together with drug therapy was necessary. Long term results with different therapeutical choices and, specifically, with the type of stimulation chosen in individual cases (sequential, rate-programmable ventricular, demand ventricular) are presented.

[His electrogram recordings in disturbances of atrio-ventricular conduction in acute ryocardial infarction (author's transl)]. / La registrazione dell'elettrogramma hisiano nei disturbi della conduzione atrioventricolare dell'infarto miocardioco acuto

48 His bundle recordings were performed on 30 patients with acute mycardial infarction and various degrees of atrioventricular block. Studies were undertaken at the time of transvenous pacemaker insertion and/or removal from the right ventricle, without pharmacological or electrical stimulation tests. The connections between site of the infarcted area and localization of the a-v block were investigated, to identify uncommon relations. Several atypical cases were observed: among 12 cases of patients with anterior infarction, 6 had prolonged P-H interval, with prolonged H-V interval in 4 cases, and normal H-V interval in the remaining 2 cases. Among the 18 cases of inferior infarction, 5 had prolonged H-V interval, 2 of which had a normal P-H interval and 3 with prolonged P-H interval. In the latter cases, the identification of a two-step a-v block by His bundle recordings was shown to be important from the clinical and prognostic viewpoint. Nevertheless, it is evident that the His bundle recording is insufficient by itself to provide any evidence of the inner pathogenetical mechanism of these phenomena, and only various hypotheses can be advanced.