An Increase in Sinus Rate Following Radiofrequency Energy Application in the Posteroseptal Space

An increase in sinus rate has been previously described in patients with AV node reentry (AVNRT) following successful A V node modification. This increase could either be a specific sign of elimination of slow pathway conduction or it could be a consequence of energy application in the posteroseptal area. Thus, we compared the changes in sinus cycle length following successful slow pathway ablation (defined as complete elimination of dual AV node physiology) in patients having AVNRT with those in patients undergoing successful ablation of a posteroseptal atriovetriricular accessory connection. Twenty five patients (16 women and 9 men, mean age 41 ± 4 years) with typical AVNRT (cycle length 378 ± 12 ms and 29 patients (16 women and 13 men, age 34 ± 5 years) with an accessory connection (17 manifest and 12 concealed) were studied. The electrophysiology study was performed during sedation with Fentanyl and Midazolam. The mean number of energy applications was 3 ± 1 for successful slow pathway ablation and 4 ± 1 for successful ablation of the accessory connection (p:NS). Following the successful energy application, the sinus cycle length decreased significantly 776 ms at baseline to 691 ms in patients with AVNRT. Following successful ablation of the posteroseptal AC, sinus cycle length decreased from 755 ms at baseline to 664 ms (p < 0.05 in both groups [difference between groups not significant]). The decrease in sinus cycle length did not correlate with the number ofRF energy applications required for successful ablation or the total energy delivered. In conclusion, ablation of the AV node slow pathway and a posteroseptal accessory connection results in similar increases in the sinus rate. Thus, the increase in sinus rate is probably due to energy application in the posteroseptal space, possibly due to concomitant destruction of vagal inputs, and it is not specific for elimination of slow pathway conduction.     

Ventilation and Heart Rate Response During Exercise in Normals: Relevance for Rate Variable Pacing

The observation of a close relationship of heart rate to oxygen uptake (HH-VO₂) and heart rate to minute ventilation (HR-VE)has been shown to be of particular value in rate variable pacing. However, the impact of anaerobic threshold (AT)for the HH-VO₂ and HH-VE slope has been studied Jess. Twenty-three male and 16 female subjects, mean age 52 ± 7 years, were selected in whom complete heart catherization and extensive noninvasive sludies excluded major cardiopulmonary disease. Semisupine bicycle exercise testing with analysis of respiratory gas exchange was performed using a ramping work rate protocol with work increments of 20 watts/min. At the respiratory AT, determined by the V slope method, oxygen uptake (VO₂-AT)was 15.2 ± 3.0 mL/kg in males versus 13.8 ± 2.3 mL/kg in females and heart rate (HR-AT)was 109 ± 18 beats/min versus 119 ± 20 beats/min, respectively. Heart rate was highly correlated (r ±0.9)to VO₂ and minute ventilation (VE). A linear regression for HR-VO₂, however, was found only in 16/39 and for HR-VE in 11/39 subjects. Assuming the AT as the breakpoint of two linear curves, it could be demonstrated that compared to low exercise HR appeared to increase at maximal exercise more in relation to VO₂ but less in relation to VE; in men the individual slopes for HR-VO₂ were 2.6 ± 0.7 below but 3.2 ± 1.0 above AT (P < 0.05) and the slopes for HH-VE were 1.6 ± 0.5 below but 1.0 ± 0,4 above AT (P < 0.05). Similarly, in women the individual slopes for HR-VO₂ were 3.7 ± 1.4 below but 4.3 ± 1.4 above AT (P < 0.05)and the slopes for HR-VE were 2.1 ± 0.9 below but 1.3 ± 0.4 above AT (P < 0.05). The differences between male and female subjects were significant. The nonlinear behavior of the HB-VO₂ and HR-VE relation from rest to maximal exercise should have a particular impact in respiratory controlied pacing systems.     

Sudden Death in Pacemaker Patients

Of 264 pacemaker patients who died within 27.6 ± 21 months following pacemaker implantation, 36 (13.6%) died suddenly. There was no difference between them and the remaining patients in terms of age, sex, indications for pacing, type of pacemaker used, and interval between pacemaker implantation and death. On autopsy, all but one patient were found to show severe three-vessel disease without evidence of acute myocardial infarction. The cause of death would thus be compatible with malignant ventricular tachycardia.     

Mobilization of CD34-positive tumour cells in a patient with testicular mixed germ cell tumour

Summary. Tumour cells from a patient with recurrent testicular germ cell cancer and bone marrow infiltration were found to express CD33 and CD34 in the absence of other haemopoiesis-associated antigens. After myelosup-pression and treatment with G-CSF for stem cell mobilization, CD34-positive tumour cells were detected in the peripheral blood in addition to normal haemopoietic progenitor cells. The tumour cells were decreased in the leukapheresis product. Retrospectively, the appearance of tumour cells in the peripheral blood after stem cell mobilization was the first indication of impending relapse.     

Heart Rate Variability During Head-up Tilt Testing in Patients with Suspected Neurally Mediated Syncope

The relation between heart rate variability (HRV) and outcome of head-up tilt testing (HUT) in patients with neurally mediated syncope (NMS) was studied in 30 patients with presumed NMS (33 ± 13 years) and in 11 age-matched controls. After 15 minutes of baseline supine observation, patients were tilted to 60± for 45 minutes or until syncope occurred. HRV parameters included RR intervals, standard deviation of normal-to-normal RR intervals (SDNN), and root mean square successive differences (RMSSD). HRV analysis was performed during 5-minute intervals in the supine position immediately after onset of HUT and before syncope or after 30–35 minutes of tilt in patients without syncope. Syncope occurred after a mean tilt duration of 32 minutes in 14 (47%) of 30 patients with presumed NMS, whereas all controls had an uneventful HUT. In the supine position, RR intervals and RMSSD were comparable among HUT-positive patients, HUT-negative patients, and controls (RR intervals: 799 ± 92, 854 ± 137, and 818 ± 128 ms, P = NS; RMSSD: 43 ± 40, 36 ± 34, and 53 ± 42 ms, P = NS). Baseline SDNN was also comparable in HUT-positive patients versus HUT-negative patients with presumed NMS (50 ± 26 vs 52 ± 20 ms, P = NS). Within 5 minutes preceding syncope or after 30–35 minutes of tilt, RR intervals and RMSSD were shorter in HUT-positive patients compared to HUT-negative patients, or to controls (RR intervals: 606 ± 86 vs 710 ± 117 and 739 ± 123 ms, P < 0.05; RMSSD: 12 ± 5 vs 23 ± 19 and 40 ± 32 ms, P < 0.05). Thus, HRV analysis in the baseline supine position was not a predictor of HUT outcome in patients with suspected NMS. Syncope during HUT seemed to be preceded by increased sympathetic activity manifested by an increase in heart rate and by a decreased parasympathetic tone manifested by a decrease in RMSSD measured for 5 minutes before the event, in comparison with HUT-negative patients and with controls.     

Assessment of Time Domain and Spectral Components of Heart Rate Variability Immediately Before Ischemic ST Segment Depression Episodes

In an attempt to study autonomic function during the 5-minute period preceding ischemic ST segment depression (↓ST) episodes, we selected 138 ↓ST episodes, without preceding ↓ST during the last 15 minutes before each episode, from the Holler tapes of 35 patients with multivessel coronary artery disease. For the 5-minute period preceding each ↓ST episode, we calculated the following heart rate variability (HRV) indices; the mean RR interval (RR5), the standard deviation of all RR intervals (SD Index5), the corresponding coefficient of variation (CV5), and the natural log (Ln) of the spectral components, total power at 0.000 to 0.400 Hz (TP5), low frequency power at 0.040 to 0.150 Hz (LF5), high frequency power at 0.150 to 0.400 Hz (HF5), and the ratio of the low to high frequency power (LF5/HF5). As HRV indices of the 24-hour period, we calculated the respective RR, SD Index, CV, LnTP, LnLF, LnHF, and Ln LF/HF. RR5, SD Index5, CV5, and LnTP5 were all significantly lower than RR (t =−5.343, p = 3.7 × 10⁻⁷), SD Index (t =−19.091, p = 1.99 × 10⁻⁴⁰), CV(t -15.780, p = 1.28 × 10⁻³²), and LnTP (t =−3.210, p = 0.0016), respectively. LnHF5 was inversely correlated with the magnitude of the ↓ST; r =−0.174, P < 0.05, and CV5 was inversely correlated with the natural log (Ln) of the ischemic event duration; r =−0.183, P < 0.05. Analogous results were obtained for both the painful and silent ↓ST episodes. It is concluded that HRV is decreased during the 5-minute period preceding ↓ST episodes, and is inversely related with the magnitude and the duration of the ↓ST.