Ventricular Research Articles

Simultaneous Atrial and Ventricular Anti‐Tachycardia Pacing as a Novel Method of Rhythm Discrimination

To evaluate a new discrimination algorithm for supraventricular (SVT) and ventricular (VT) tachycardias, based on the response to simultaneous (A+V) atrial (A) and ventricular (V) anti-tachycardia pacing (ATP). Patients undergoing electrophysiological testing or dual-chamber implantable cardioverter-defibrillator (ICD) implantation were enrolled (N = 32) and underwent A+V ATP through a Marquis ICD with investigational software. If persisting after ATP, the rhythm was classified as VT if the first electrical event was sensed on the V channel and as an SVT otherwise. Arrhythmia sequences (N = 275; 53 VT; 222 SVT) were analyzed in 26 patients (age = 51 +/- 17 years, 13 men, LVEF = 0.49 +/- 0.14). In response to A+V ATP, 55% of SVT versus 41% of VT episodes were terminated (P = NS). Termination of VT but not of SVT was more likely with faster (50% at ATP/arrhythmia cycle length (CL) = 0.81 vs 8% at ATP/arrhythmia CL = 0.88, P = 0.02) but not with longer ATP bursts (P = NS). Of the 115 arrhythmias that persisted after A+V ATP, the algorithm correctly classified 24 of 24 VT (GEE-adjusted sensitivity = 100%) and 85 of 91 SVT (GEE-adjusted specificity = 93%). Proarrhythmia was noted after two A+V ATP, in the form of atrial fibrillation induction and VT acceleration. We describe a new algorithm that can discriminate between SVT and VT with a high sensitivity and specificity. This form of ATP can terminate 55% of SVT sequences. The performance of this new algorithm merits further testing in a large population of dual-chamber ICD patients.

Holter ECG Monitoring during Research Bronchofiberoscopy in Patients with Asthma

Bronchoscopy is a very useful tool in asthma research studies. The study was undertaken to evaluate the effect of bronchoscopy, BAL and bronchial biopsies on heart rate and arrhytmias in patients with asthma. Twenty patients (12 M, 8 F, mean age 39,6+/-16,3 yrs) with asthma (mean FEV, 81+/-19.5% pred.; mean FEV(1)%VC 69+/-12.3%) participated in the study. Holter ECG monitoring was performed twice: before (1 or 2 days) and on the day of bronchoscopy. Heart rate and cardiac arrhythmias were compared to prebronchoscopy recording at four separate time intervals: during bronchoscopy, first postbronchoscopic hour, second postbronchoscopic hour and total 24 hours. There were no significant differences between mean heart rate at the time of bronchoscopy (88.5+/-14.1 min(-1) vs 83.7+/-11.9 min(-1)), first and second postbronchoscopic hour (80.9+/-15.8 min(-1) vs 85.7+/-13.7 min(-1) and 82.6+/-13.6 min(-1) vs 80.6+/-11.6 min(-1)) as well as total 24 hours (76.1+/-11.2 min(-1) vs 75.9+/-9.4 min(-1)) as compared to prebronchoscopic recordings. Max. heart rate during bronchoscopy was higher as compared to the corresponding time of prebronchoscopic recording (134.5+/-11.5 min(-1) vs 122.5+/-19.6 min(-1), p<0,05). No differences in the number and type of ventricular (VA) and supraventricular arrhythmias (SVA) between the pre- and peribronchoscopic monitoring were observed. Positive correlation between the age and the number of VA during bronchoscopy has been found. Bronchoscopic procedures in asthma patients do not increase the risk of cardiac arrhythmias. Some factors influencing the heart rate and number of VA during bronchoscopy can be identified.

Automatic ectopic beat elimination in short-term heart rate variability measurement

Our studies deal with fully automatic measurement of heart rate variability (HRV) in short term electrocardiograms. Presently, all existing HRV analysis programs require user intervention for ectopic beat identification, especially of supraventricular ectopic beats (SVE). This makes the HRV measurement in large, e.g. epidemiological studies problematic. In this paper, we present a fully automatic algorithm for the discrimination of the ventricular (VE) and SVE ectopic beats from the normal QRS complexes suited for a reliable HRV analysis. The QRS identification is based on the template matching method. The ectopic beats are identified based on several morphological and timing properties of the electrocardiogram (ECG) signal. The method incorporates several approaches and makes HRV analysis of large numbers of electrocardiograms feasible. It uses the template matching for the basic morphology check of the QRS complex and the P-wave, the timing information to avoid unnecessary ectopic beat checks and to adjust thresholds and it also looks for a special QRS morphology, which is common in VEs. We used a testing set of 69 electrocardiograms selected from a large number of recordings. The selected ECGs contained abnormalities including ectopic beats, right branch bundle block, respiratory arrhythmia, blocked atrial extrasystole, high amplitude and wide T-waves. The evaluation of our method showed a specificity of 0.99, supraventricular ectopic beat sensitivity of 0.99 and ventricular ectopic beat sensitivity of 0.98.

The Hemodynamic and Holter-Electrocardiogram Changes During Halothane and Sevoflurane Anesthesia for Adenoidectomy in Children Aged One to Three Years

The Hemodynamic and Holter-Electrocardiogram Changes During Halothane and Sevoflurane Anesthesia for Adenoidectomy in Children Aged One to Three Years

992–114 Atrial Recordings for the Differentiation of Ventricular and Supraventricular Tachyarrhythmias

Inappropriate shocks due to supraventricular tachyarrhythmias (SVT) are a major concern in patients with implanted defibrillators. To elucidate the role of atrial recordings for the differentiation of ventricular (VT) and SVT, 127 right and left epicardial atrial electrograms were simultaneously recorded during atrial fibrillation (AF), ventricular fibrillation (VF), and rapid ventricular pacing (VP) at the fastest rate with retrograde 1:1 conduction simulating VT in 4 dogs with sterile pericarditis. Mean atrial (ACI) and ventricular cycle-lengths (VCI) were determined before and during adrenaline infusions (1.0 μ g/kg/min). Adrenaline was given to stimulate physical exercise. In 43 ± 10% of all atrial recordings, the atrial signal was contaminated by ventricular activity of similar or higher amplitude. Due to a smaller ventricular signal, this was only true for 28 ± 11% (* p &lt; 0,05) of atrial recordings during VF. At selected atrial sites, monophasic atrial signals turned into fragmented electrograms or double potentials with short ACI, due to local conduction delay or block. Thus, apart from “true” ACI measured at sites with clear atrial signals, “false” ACI were measured at electrode sites with complex local activity and/or ventricular interference. Data are summarized in the table below. Control Adrenaline CI (ms) True ACI False ACI VCI True ACI False ACI VCI AF 112 ± 20 * 105 ± 18 319 ± 92 97 ± 18 * 90 ± 17 290 ± 81 VP 343 ± 86 172 ± 64 * 343 ± 86 327 ± 75 163 ± 59 * 327 ± 75 VF 426 ± 93 107 ± 26 121 ± 23 * 358 ± 56 101 ± 27 114 ± 21 * * p &lt; 0.05 ACI clearly differentiates VT and SVT even during adrenaline stress. However, superimposed ventricular activity or tachycardia-dependent complexities of the atrial signal impose a substantial risk of false detections.

Active Fixation Leads—Long‐Term Threshold Reduction Using a Drug‐Infused Ceramic Collar

Previous investigators, including our group, have reported the threshold reduction benefits of steroid-releasing leads. To date, all published literature has been for the passive fixation versions. The application of steroids should also enhance the performance of active fixation leads. We have developed and tested an atrial and a ventricular Accufix lead with a dexamethasone acetate-releasing, porous ceramic collar (DA DEC). A long-term sheep study has shown a significant reduction in thresholds (THR) when compared to standard Accufix leads without the collar (ACC) for atrial (ATR) and ventricular (VENT) versions (bipolar THR [0.5 msec] at 24 weeks: VENT DA DEC = 0.51 +/- 0.07, VENT ACC = 1.49 +/- 1.03; ATR DA DEC = 1.31 +/- 1.14, ATR ACC = 2.99 +/- 1.31). All other parameters tested, including pacing and sensing impedance as well as polarization overpotential, were similar for the two groups. The Accufix DEC leads therefore have excellent potential for low energy stimulation.

Subthreshold electrical stimulation for termination and prevention of reentrant tachycardias.

Subthreshold electrical stimulation (STS) was used to terminate and prevent reentrant supraventricular and ventricular (VT) tachycardia. Of 12 patients with SVT, 8 had atrioventricular nodal (AVN) reentry, and 4 had orthodromic tachycardias. Trains of STS applied close to the AVN area terminated the tachycardias in five of the eight patients with AVN re-entry and two of the patients with orthodromic tachycardia. In 13 patients with recurrent sustained hemodynamically stable VT (mean cycle length 370 +/- 40 ms), trains of STS were delivered at the site of early activity during the tachycardia. Number of train cycles ranged between 3 to 8 pulses and their cycle lengths ranged between 20 and 70 ms. In 7 of the 13 patients VTs were effectively terminated by STS application close to the site of early activity and in the remaining 6 patients it did not. In nine patients the effect of STS applied at the site of early activity on VT induction from the right ventricular apex was examined. In four of the nine patients STS prevented VT induction and in the remaining five patients it did not. These observations suggest that STS applied in proximity to the area critical for initiation and maintenance of reentry can terminate or prevent induction of the tachycardia.

Transcutaneous pacing: Patient tolerance, strength-interval relations and feasibility for programmed electrical stimulation

Noninvasive transcutaneous pacing has been used successfully in situations requiring emergent ventricular pacing, 1–8 and has also been used to terminate ventricular (VT) or supraventricular tachycardia in some patients. 9–13 Thus, transcutaneous pacing might logically be considered a suitable noninvasive substitute for endocardial pacing during programmed electrical stimulation studies. We therefore determined the following features of transcutaneous pacing using the Zoll noninvasive temporary pacemaker (Zoll NTP, ZMI Corp.): patient tolerance, which cardiac chambers were paced, the ventricular effective refractory period (ERP) compared with that determined by endocardial pacing and feasibility for programmed electrical stimulation in patients with ventricular tachyarrhythmias.

A Simple Echocardiographic Method to Detect Atrioventricular Dissociation: A Useful Aid in the Differential Diagnosis of Regular Tachycardia with Wide QRS Complexes

Regular tachycardia with wide QRS complexes may be difficult to classify as supraventricular (SVT) or ventricular (VT) without electrophysiologic studies. We felt that hemodynamic differences between VT and SVT should allow their distinction by echocardiography. In this study, we utilized high speed M-mode echocardiography in the usual projections in eight patients during tachycardia. Two patients had spontaneous VT and three had spontaneous SVT with aberrant conduction. The remaining three were patients in sinus rhythm undergoing electrophysiologic studies in whom right ventricular (RV) pacing (induced VT), right atrial (RA) pacing (induced SVT) and sequential RV-RA pacing (induced VT with 1:1 retrograde conduction) were carried out. The echocardiographic parameters studied included: left ventricular internal dimensions, time during which the mitral valve remained open (MVOT), left ventricular ejection time (LVET) and pre-ejection period. We measured 20 consecutive beats and for each parameter defined its variability. During A-V dissociation (VT, RV pacing) there was always a striking beat-to-beat variability in the values of MVOT (68 percent to 129 percent) and in LVET (41 percent to 175 percent). In contrast, during A-V association (SVT, sequential RV-RA pacing, sinus rhythm) the maximal variability of MVOT and LVET was 22 percent and 12 percent, respectively. Variability during A-V dissociation could be explained by asynchronous timing of atrial systole. We conclude that echocardiography can readily identify atrioventricular dissociation, a feature heavily in favor of a diagnosis of VT.

Carbachol, angiotensin-II, ventricular spread and water balance in rats

Injections into the preoptic areas and anterior hypothalamus of as little as 1.0 ng/μ1 carbachol (5.5 × 10 −6M, 11 pmols total dose) and 0.1 ng/μ1 angiotensin-II (10 −7M, 0.2–0.4 pmols) were dipsogenic or antidiuretic-natriuretic. Lateral ventricular (VL) threshols for drinking also were 11 pmols for carbachol and 0.2 pmols for angiotensin. The low VL threshold for carbachol supports, without proviing, arguments that a limbic cholinergically-coded thirst circuit could reflect leakage form placements near VL to the third ventricle. In contrast, VL thresholds for antidiuresis-natriuresis were 110 pmols for carbachol and 2 pmols for angiotensin. Carbachol was more effective rostral to the paraventricular nucleus and angiotensin dorsal to the supraoptic nucleus. However, lower thresholds in these areas were insufficient to localize receptors, since all cannulas positive for antidiuresis-natriuresis traversed ventricles, and cannulas not traversing ventricles were negative.