Atrial Pacing Method Research Articles

Differential Atrial Pacing to Detect Reconnection Gaps After Pulmonary Vein Isolation in Atrial Fibrillation.

High-resolution mapping is useful to identify reconnection gaps in the pulmonary vein after pulmonary vein isolation for atrial fibrillation. However, it is sometimes difficult to differentiate pulmonary vein potentials from far-field potentials because of very low amplitudes. Our purpose was to evaluate the usefulness of a novel differential atrial pacing method to differentiate reconnected pulmonary vein potentials from isolated pulmonary vein potentials. This retrospective observational study included 34 patients with atrial fibrillation (22 men; mean age, 64 ± 14 years; 28 with paroxysmal atrial fibrillation) who underwent radiofrequency or cryoballoon ablation. Following pulmonary vein isolation, we created a high-resolution activation map during pacing from both the coronary sinus and left atrial appendage. We compared the characteristics of the pulmonary vein potentials and the pattern of activation between the reconnected and isolated pulmonary veins. We analyzed 131 pulmonary veins and found reconnections in 41 pulmonary veins (R group); 90 pulmonary veins had no reconnection (NR group). The R group had a significantly shorter distance between the earliest pulmonary vein activation sites in both activation maps, compared with the NR group (5.22 ± 0.53 mm versus 17.08 ± 0.36 mm, respectively; P < 0.0001). The amplitude of the pulmonary vein potentials was higher in the R group versus the NR group (0.61 ± 0.05 mV versus 0.04 ± 0.03 mV, respectively; P < 0.0001). Six gaps (14%) in the R group that were unrecognized using a conventional method were identified using our novel method. In conclusion, differential atrial pacing was useful to identify pulmonary vein reconnection gaps during ablation using a novel high-resolution mapping system.

Temporary neonatal atrial pacing through the umbilical venous route: A novel technique

Atrial pacing in the neonate is rarely done due to constraints of equipment, technical knowhow, and risk of complications. We describe a novel method of atrial pacing in the new born using equipment readily available in any intensive care unit. Atrial pacing can be achieved using an adult bipolar pacing wire directly introduced through the umbilical venous route. We have used this method in 5 neonates, and achieved atrial capture in 4 patients. Temporary atrial pacing is a therapeutic option in a few neonatal arrhythmias, such as atrial flutter, a few types of re-entrant tachycardias, such as accessory pathway mediated tachycardia and junctional reciprocating tachycardia, and has a limited role in cardiopulmonary resuscitation where sinoatrial node dysfunction is suspected.

Halothane‐Anaesthetized, Closed‐Chest, Guinea‐Pig Model for Assessment of Drug‐Induced QT‐Interval Prolongation

For the halothane-anaesthetized, closed-chest, guinea-pig model, corrected QT interval (QTc) has been empirically used to estimate the extent of drug-induced QT-interval prolongation. In the present study, we employed an atrial pacing method to clarify a net effect of a drug on the QT interval in this model. The atrial pacing catheter was inserted via the jugular vein with a minimal surgical invasion, and the effects of d-sotalol (0.3 and 3 mg/kg, intravenously) and verapamil (0.01 and 0.1 mg/kg, intravenously) on electrocardiogram parameters were assessed under the sinus rhythm and during the atrial pacing of 200 and 240 beats/min. d-Sotalol significantly prolonged the QT interval in a reverse use-dependent manner and decreased the heart rate, while verapamil prolonged the PR interval without affecting the heart rate or QT interval, indicating the sensitivity and specificity of this model in assessing the pharmacodynamics of the drug-induced QT-interval prolongation. Using the QT/RR relationship under the sinus rhythm, we obtained the following two types of QT-interval correcting formulae; namely, QTc = QT - 0.207(RR - 300) by a linear regression method; and QTc = QT/(RR/300)0.332 by a non-linear regression method, the latter of which is equal to 0.67 times of Fridericia's formula, providing rationale for the use of mathematical correction in this model. Thus, the halothane-anaesthetized, closed-chest, guinea-pig model may be highly useful for assessing the drug-induced QT-interval prolongation, which may become an alternative to current models for the in vivo QT assay.

Regional right and left atrial activation patterns during single- and dual-site atrial pacing in patients with atrial fibrillation

We examined the activation of the right atrium and left atrium by pacing from different atrial sites using several single- and dual-site atrial pacing modes in patients with atrial fibrillation or flutter. We also analyzed the effect of these pacing modes on fixed coupled extrastimuli in this population. Patients underwent detailed mapping of regional right atrial (RA) and left atrial (LA) sites. Bipolar pacing was performed individually from the high right atrium, coronary sinus ostium, and the distal coronary sinus, and simultaneously from the high right atrium and coronary sinus ostium (dual-site RA pacing) or high right atrium and distal coronary sinus (biatrial pacing). Extrastimuli were delivered from the high right atrium at fixed coupling intervals of 350 and 250 ms. Twenty patients with atrial fibrillation were studied. P-wave duration during pacing was significantly abbreviated by both dual-site RA and biatrial pacing (p < 0.001 vs high RA pacing, respectively) but not by any other single-site atrial pacing method. Both dual-site atrial pacing modes also significantly abbreviated P wave durations for closely coupled high RA premature beats (p < 0.001) in contrast to high RA pacing. During the basic pacing drive and for high RA extrastimuli, RA activation at the crista terminalis and atrial septum was comparable in sinus rhythm, high RA pacing, and in both dual-site atrial pacing methods, but was significantly delayed by coronary sinus ostial and distal coronary sinus pacing. In contrast, proximal coronary sinus activation was delayed with high RA pacing compared with all other pacing modes, and high RA extrastimuli encountered reduced conduction delay at this location with dual-site atrial pacing modes. LA activation was advanced superiorly by both single-site coronary sinus pacing methods and both dual-site atrial pacing techniques. Inferior and lateral LA activation was advanced by all pacing modes using a coronary sinus pacing site. However, earlier activation of LA sites occurred for high RA premature beats after both dual-site pacing methods (p < 0.05) compared with single-site pacing modes. Incremental conduction delay at different atrial regions for closely coupled high RA extrastimuli ranged from 33% to 120% during high RA pacing and was significantly attenuated at multiple RA and LA sites by dual-site RA and biatrial pacing. Distinct global, as well as regional electrophysiologic effects, may mediate the variable antiarrhythmic effects of different and novel atrial pacing methods.

Impedance to Transesophageal Atrial Pacing: Significance Regarding Power Sources

Transesophageal stimulation is an expeditious method of atrial pacing. Using pulse widths of 10 msec results in reduction of current requirement to values that are usually less than 15 mA. An unknown variable in transesophageal atrial pacing has been impedance. In this study, we investigated the impedance to transesophageal atrial pacing in ten patients using a stimulator with a 63 V power source capable of delivering constant current to 20 mA against an impedance of 2,000 ohms. A bipolar electrode was used to deliver stimuli with a current of 15 mA. Voltage across a known resistance and current were measured on an oscilloscope and the impedance was calculated. Pacing thresholds were also performed and ranged from 6.2 to 16.5 mA (mean 9.4 +/- 2.9 mA, SD). Impedance varied between 720 and 2,670 ohms (mean 1,750 +/- 540 ohms). The stimulator used to measure impedance in man and two other commercially available stimulators were bench tested against known resistances of 500 to 2,000 ohms. The other stimulators with power sources of 12.5 and 15 V had attenuation of the delivered current at resistances of between 1,000 and 2,000 ohms. Thus, this study has demonstrated that transesophageal atrial pacing incurs impedances two to five times greater than incurred with intracardiac pacing leads. Therefore stimulators with high power sources are required to deliver the programmed current against these impedances.

Unusual Cardiac Complications of Wegener's Granulomatosis

Wegener's granulomatosis most commonly involves the sinuses, lungs and kidneys with necrotizing granulomatous vasculitis. In 12 percent of a large series of patients with Wegener's granulomatosis there was cardiac involvement, largely manifested by pericarditis and coronary arteritis. We present three patients with this disease who developed unusual cardiac complications. Patient 1 had renal failure requiring hemodialysis, pericardial tamponade requiring pericardiocentesis, and later developed constrictive pericarditis requiring pericardiectomy. Patient 2 developed pericarditis and high grade atrioventricular block, and patient 3 developed pericarditis and atrial tachycardia resistant to pharmacologic and transesophageal atrial pacing methods. All three patients greatly improved with cyclophosphamide therapy. The rhythm disturbances seen in patients 2 and 3 were attributed to coronary arteritis. The renal failure in patient 1 was due to Wegener's granulomatosis, but whether the constrictive pericarditis was due to uremic pericarditis or the pericarditis of Wegener's granulomatosis is uncertain. As patients with Wegener's granulomatosis live longer with cyclophosphamide therapy and because inpatient arrhythmia monitoring and recording has become more widespread, these uncommon manifestations of Wegener's granulomatosis may be seen more often.

Sinus node responses to perfusion pressure changes, ischaemia and hypothermia in the isolated blood-perfused dog atrium.

Sinus node responses to perfusion pressure changes, ischaemia and hypothermia were evaluated in 22 isolated blood-perfused dog atria. Sinus cycle length (SCL) was measured and sinoatrial conduction time (SACT) was estimated using the premature atrial stimulation technique (PAS) and the constant atrial pacing method (CAP). There was a good correlation between the results obtained with both techniques (r = 0.8297) but CAP had less depressing action on sinus node automaticity. Increasing the perfusion pressure from 100 to 200 mmHg did not influence estimated SACT nor SCL. However, a reduction in perfusion pressure (from 100 to 50 mmHg) markedly shortened SCL without significantly decreasing estimated SACT. Lowering temperature from 37 to 25 degrees C caused a linear increase in estimated SACT and SCL. Occlusion of the sinus node artery induced a sinus tachycardia which was not blocked by sotalol. Estimated SACT was significantly shorter 1 min after occlusion and longer 3 min after occlusion; this increase was significantly inhibited by atropine infusion. Thus, the increase in estimated SACT seen after occlusion might be related to cholinergic activity. However, the sinus tachycardia following a decrease in perfusion pressure might be due to activation of the stretch-receptors while the one seen after reduction in blood flow and occlusion of the sinus node artery seems more likely to be a consequence of ischaemia.

Premature atrial stimulation during regular atrial pacing: A new approach to the study of the sinus node

Using an induced premature atrial depolarization after atrial pacing for 8 beats to scan the postpacing cycle, sinus node (SN) response was studied in 23 patients and the results were compared with those obtained using the Strauss method. Late extrastimuli resulted in compensatory return cycles (zone I), increasing prematurity gave rise to less-than-compensatory return cycles (zone II or “plateau”) and interpolation or echo responses occurred at shorter coupling Intervals (zone III). The sinoatrial (SA) conduction time was defined as the difference between return cycle and postreturn cycle lengths that fell in the latter portion of zone II. The SA conduction time was similar to those derived from the Strauss method (r = 0.91, n = 17, p < 0.01) and remained similar at the 2 pacing cycles, 172 ± 52 ms (mean ± standard deviation) at 739 ± 71 ms (cycle 1) and 170 ± 60 ms at 596 ± 57 ms (cycle 2). In 4 patients, the atrial pacing method could unmask zone II. The SN refractory period was defined as the longest coupling interval at which zone III was apparent. It was compared at cycles 1 and 2 in 14 patients. There was a significant increase in the SN refractory period with faster pacing rates, from 406 ± 104 ms (cycle 1) to 462 ± 112 ms (cycle 2) (p < 0.05). The atrial pacing method provides an alternative evaluation of SA conduction and may permit the study of drug effects at identical basic rates.

ATRIAL PACING TO ESTIMATE SINOATRIAL CONDUCTION TIME IN CHILDREN

s)with those generated by the atrial pacing method (TSACT N).In this study, TSACT in 55 patients, age 0.5, was measured using both techniques . TSACTN was performed at a mean 90% (TSACTN-90) (n= 32)or a mean 95% (TSACT N _45and(n = 38) of sinus cycle length (SCL) . When data generated during determination of TSACT N _94and TSACTswere compared, SCL and recovery cycle length (REC) were similar for both techniques . Likewise, TSACTs (128 ± 40 ms) and TSACT N_94(126 ± 74 ms) were not significantly different . Coefficient of correlation was r =0.82, p < 0.001. Chi-square analysis demonstrated a strong association of normal and abnormal values between TSACT $and TSACTN_90.In contrast, when values generated during TSACTN-95 and TSACTswere compared, TSACT sexceeded TSACT N_95(137 ± 38 vs 105 ± 58 ms; p< 0.001) . Values for SCL and REC were similar while correlation between TSACT determined by the two techniques remained strong (r =0.82, p <0.001) . Despite a good correlation between TSACT N _90and TSACTs,individual differences in magnitude and direction were noted between the two techniques . In summary, TSACT N_90 approximates TSACT sin children . TSACTN_ 90is preferable to TSACT N_95,probably due to more complete sinus node capture during atrial pacing . However, the behavior of the sinus node in response to extrastimuli (single or train) precludes favoring one technique over the other . More precise evaluation of sinoatrial conduction will require direct recording of sinus node activity

Effects of dopamine on sinoatrial conduction in isolated, blood-perfused dog atria.

Dopamine, administered at a constant infusion rate of 1-2 micrograms/min into the cannulated sinus node artery of the isolated dog atrium, decreased sinus cycle length (SCL) from 630 +/- 19 to 501 +/- 22 msec (mean +/- SEM, 38 trials in 12 atria). However, on sinoatrial conduction time (SACT) estimated by a constant atrial pacing method, dopamine produced 2 types of response (shortening and lengthening) with sinus tachycardia. In 24 trials in 11 atria, the drug decreased SACT from 86 +/- 8 to 56 +/- 4 msec, and in 14 trials in 6 atria it increased SACT from 67 +/- 7 to 101 +/- 9 msec. In general, the effects of dopamine on SACT were dependent on the control levels of SCL: dopamine caused a reduction of SACT at small levels of SCL and a prolongation at large levels. At a control sinus rate of 120 beats/min, dopamine usually shortened SACT. Dopamine-induced shortening of SACT was blocked by a beta-adrenoceptor blocker, propranolol, and an uptake blocker, imipramine, but not by a dopaminergic inhibitor, sulpiride. Furthermore, dopamine-induced lengthening of SACT tended to be suppressed by propranolol, but not by sulpiride. It is concluded that the dopamine-induced changes in SACT are mediated via beta-adrenergic mechanism and partially due to a tyramine-like action.

Therapeutic uses of permanent pervenous atrial pacemakers: A review

The available techniques for permanent pervenous atrial pacing have been reviewed with particular emphasis on the coronary vein approach. The major therapeutic uses for permanent atrial pacing include sinus node dysfunction, recurrent ventricular tachyarrhythmias, and intractable supraventricular tachycardias. Special types of atrial pacing involve the use of bifocal atrioventricular sequential pacing, paired atrial pacing, and rapid atrial pacing generators. The potential problems associated with the coronary vein atrial pacing method are discussed.

Alternate Patterns of Premature Ventricular Excitation during Spontaneous Atrial Bigeminy

This report documents two instances of spontaneous alternate patterns of premature ventricular during atrial bigeminy (alternating premature ventricular excitation). Previous reports of alternating premature ventricular excitation have required control of electrophysiologic parameters by atrial pacing methods. Illustration of this arrhythmia and a discussion of its mechanism constitute the substance of this report.

Permanent Pervenous Atrial Pacing from the Coronary Vein

Permanent pervenous atrial pacing from the coronary vein has been attempted in 14 patients. Several types of arrhythmias including symptomatic bradycardia, "bradytachy" syndrome, and refractory ventricular tachyarrhythmia-fibrillation have been successfully treated with pervenous atrial pacing in 10 patients for 1 to 30 mo. Longterm atrial pacing was unsuccessful in four patients; in two of these four this was due to high atrial pacing thresholds. To date there has been no evidence of pacemaker perforation or pacemaker-induced coronary vein thrombosis. It is concluded that permanent pervenous atrial pacing from the coronary vein is a reliable method of atrial pacing without resorting to thoracotomy.

Hemodynamic Effects of Nitroglycerin in Patients with Angina Pectoris Studied by an Atrial Pacing Method

The hemodynamic effects of nitroglycerin on 20 patients with coronary arterial disease were assessed by using atrial pacing to invoke angina pectoris. This new technique also permitted study of the hemodynamics during pain without the interference of the effects of muscular exercise on the heart affected by coronary artery disease. The pain threshold of each patient was determined by successive pacing runs and the effects of nitroglycerin were evaluated both before and during the pacing up to the level of pain. With regard to the circulatory status at pain an abnormally elevated pulmonary capillary venous "wedge" pressure was an infrequent phenomenon. This difference from the data of studies in which muscular exercise is used is briefly discussed. Sublingual nitroglycerin decreased aortic, pulmonary arterial, right atrial, and pulmonary capillary venous pressures. Stroke volume and cardiac output were reduced and this reduction was accompanied by a compensatory rise in heart rate. Tension-time index was reduced and during pacing at identical rates never reached the level at which angina pectoris was experienced before nitroglycerin. End-diastolic heart size as estimated from conventional chest roentgenograms was reduced by nitroglycerin at every pacing step in all six patients studied by this method. The conclusions were that at all heart rates studied nitroglycerin (a) decreased atrial pressures, (b) decreased heart size, (c) caused peripheral vasodilatation, and (d) allowed the heart to be driven at a higher rate without production of anginal pain. These hemodynamic changes reflect a decreased oxygen requirement of the heart and are consistent with the pain-relieving properties of nitroglycerin.