Bipolar Lead Research Articles

Comparison of Unipolar and Bipolar Active Fixation Atrial Pacing Leads

The purpose of this investigation was to compare the acute pacing and sensing characteristics of a new bipolar active fixation atrial pacing lead with those of a unipolar atrial lead of similar design. Pacing threshold voltage and current, lead impedance, and atrial electrogram amplitude and slew rate were measured at the time of surgery in 28 consecutive patients undergoing DDD pacing system implantation. Eleven patients received a Medtronic 6957J-58 unipolar active fixation atrial lead and 17 patients were given a Medtronic 4016-58 bipolar lead. Both leads are polyurethane-insulated with the distal electrode being a platinum alloy screw-helix with a surface area of 8.0 mm2. There were no significant differences in the threshold voltage (1.01 V unipolar versus 1.05 V bipolar) or current (1.93 mA unipolar versus 1.78 mA bipolar) of the two leads. The mean impedance of the bipolar active fixation lead was 618 ohms compared to 479 ohms for the unipolar lead (p = 0.02). The mean amplitude of the atrial electrogram was 4.64 mV for the bipolar lead and 3.11 mV for the unipolar lead (p = 0.02). The atrial electrogram exceeded 5 mV in 10 of 17 patients with the bipolar lead but zero of 11 with the unipolar lead. There was no significant difference in the mean slew rate of the leads (1.09 V/s bipolar versus 0.73 V/s unipolar; p = 0.18). Over a follow-up period of up to 10 months, all patients remained in either the DDD or DDI modes with no episodes of atrial sensing or pacing failure.(ABSTRACT TRUNCATED AT 250 WORDS)

牛の胎児心電図の誘導部位

As a reference, the fetal electrocardiogram was recorded in 57 Holstein cows for the period from two months to two days before deliverey. Then in a similar manner, the electrocardiograms were recorded far the twin fetuses carried by 10 pregnant cows, which were either superovulated mothers raised in Kanagawa Prefecture or cows from Fukusima Prefecture that were transplanted with two cleaved eggs. A comparative study of the ECCs gave the followingfindings:1. The highest ratio (92%) of successful fetal ECG recordings was obtained when the leads were set on the abdominal wall above and below, or to the right and left, of the intersection between the vertical line from the 4th lumbar vertebra and the horizontalline traversing the knee joints. The recording was less successful as the leads were set farther from these sites.2. The QRS potentials were highest at the above-mentioned sites: the highest reached 85μV for the above/below lead configuration and 94μV for the right/left lead configuration.3. The diagnosis of twin gestation was established by the same bipolar lead electrocardiography as conducted on cows with a single fetus (Refer to1 in the summary). In one case, however, twins were delivered despite the prenatal diagnosis of monofetal gestation based on the ECG findings, though in this case the fetal heart rate had differed between the above/below and the right/left recording positions. The occurrence of this misdiagnosis suggests that ECGs should be recorded simultaneously through multiple channels and that the recording should be repeated, since the fetal presentation changes as time passes.

Validation of a real-time electrocardiographic monitor for detection of myocardial ischemia secondary to coronary artery disease

A new real-time electrocardiographic (ECG) monitor (QMED Monitor One TM) was evaluated to assess its accuracy in detecting ischemic ST-segment changes in 43 patients (34 men, 9 women, mean age 56 ± 11 years) during exercise stress testing. The output of QMED was compared with ST-segment measurements from a Marquette CASE-II computer (ECGM) using a bipolar lead CM 5, defining a positive ECG as at least 1 mm of planar or downsloping ST depression. Results were concordant in 33 patients, 15 with both positive and 18 both negative responses, yielding an accuracy (expressed as sensitivity, specificity, positive and negative predictive accuracy) of 83%, 72%, 68% and 86%, respectively. Seven false-positive QMED episodes occurred: 4 due to excess baseline wander or noise in the control ECG, which may have been prevented by reapplication of electrodes, and all 7 episodes were correctly discounted by inspection of the sample ischemic ECG output, yielding an accuracy of 81%, 100%, 100% and 85%. Mean duration and maximal magnitude of ST depression in patients with a positive ECG response was 7.9 ± 7 minutes and 1.7 ± 0.6 mm for QMED and 8.9 ± 7 minutes and 2.2 ± 0.7 mm for ECGM. The 3 false-negative QMED events were relatively brief and mild ischemic episodes and slight differences in electrode placement between the 2 systems may account for this discrepancy in 2 of the patients. Real-time ST monitoring with QMED is sufficiently reliable for clinical use. Optimal specificity depends on the ability to inspect sample ECG traces to verify a stable baseline and confirm episodes of ischemic ST-segment shift.

Method for Antegrade/Retrograde Conduction Discrimination Using A Standard Atrial Bipolar Lead

Significant differences between morphology, magnitude, and relative timing of antegrade and retrograde conduction were demonstrated on unipolar electrograms from a standard atrial bipolar J lead positioned in the right atrium in dogs. The morphology of the P wave sensed from the tip was more or less biphasic while the morphology of the P wave sensed from the ring was monophasic only and of lower frequency content. The unipolar-ring P wave was attenuated in retrograde as compared with the antegrade. During retrograde conduction the unipolar-ring signal returned to baseline earlier in time relative to the peak of the unipolar-tip signal, than it did during antegrade conduction. Based on these differences a sensing circuit capable of discriminating between antegrade and retrograde conduction was built. This discriminator circuit, which relies on a standard lead and simple electronics, functioned reliably in trials in dogs and thus may prove to be practical for use in future pacemakers.

Early electrocardiographic diagnosis of left ventricular hypertrophy in hypertensive patients

This study included 25 hypertensive patients with “normal” standard 12-lead scalar electrocardiogram and an equal number of age- and sex-matched controls. We recorded routine twelve leads, posterior chest leads, ensiform lead, right-sided precordial leads, lead CM 5 and oesophageal electrocardiogram at different levels in all individuals. In addition we recorded an unconventional unipolar lead with the chest electrode placed on the thoracic seven spine. We also recorded some unconventional bipolar leads, in each instance using V 5 as the positive electrode and the T 7 spine, or the oesophageal electrode as negative. We observed that the T wave height of 20% or less of R wave amplitude in lead I was highly specific (92%) and sensitive (76%) in detecting early left ventricular hypertrophy in hypertensive patients, with the standard 12-lead electrocardiogram considered “normal” by conventional criteria. The T wave amplitude of 15% or less of the accompanying QRS in lead V 6 was nearly equally diagnostic (specificity 88% and sensitivity 68%). An S wave of 0.3 mV or more in the bipolar lead recorded with the positive electrode at V 5 and the negative electrode on T 7 spine was also highly specific (80%) and sensitive (72%). Isoelectric or inverted T wave in lead V 8, ST segment depression and T wave inversion in lead CM 5 and ST segment depression in the bipolar lead recorded with the positive electrode at the V 5 position and negative electrode at the atrial level of the oesophagus were highly specific (100%) but had a low sensitivity (40, 36, 16, and 28%, respectively). Combined lead V 8 and lead I further improved the sensitivity to 96% without decreasing the specificity.

Evaluation of esophageal electrodes for recording His-Purkinje activity based upon signal variance.

Signal averaging the ECG to observe low level signals generated by His-Purkinje system (HPS) has many disadvantages and has not been widely used. This is partly due to the inability to distinguish between atrial and HPS potentials within the PR segment. To more clearly observe the onset of the HPS activity, several leads with an esophageal electrode were studied and compared to a bipolar surface lead. Signal variance was calculated to estimate the noise levels present in all lead systems. The bipolar surface lead consistently provided reproducible HPS waveforms with accurate estimates of noise levels. The leads with an esophageal electrode (bipolar or esophago-thoracic) failed to show reproducible HPS waveforms and had higher noise levels than the bipolar surface lead as measured by signal variance. The cause of these problems is the motion of the electrode within the esophagus, as visualized fluoroscopically. While the novel lead systems were not adequate for recording HPS waveforms, the analytic methods for evaluating signal averaged recordings from various lead systems provided a basis for optimizing this approach for quantifying low level cardiac signals.

Value of the bipolar lead CM5 in electrocardiography.

Only bipolar lead recording are available during ambulatory monitoring. Their sensitivity in detecting ST segment changes in relation to standard electrocardiographic leads is not known. The magnitude and direction of ST segment changes in the bipolar lead CM5 were compared with those in standard electrocardiographic leads in patients during exercise testing and percutaneous transluminal coronary angioplasty. Thirty patients with coronary artery disease were studied during exercise tests in which ST segment depression (greater than 0.5 mm) occurred in one or more standard electrocardiographic leads and 13 patients were studied during angioplasty that resulted in ST segment change in one or more leads (I, II, III, V2, V5, and CM5). Lead CM5 was the most sensitive lead (93%) during exercise testing and also showed the greatest magnitude of ST segment change below the isoelectric line in 93% of the patients. Only two patients, one with ST segment elevation in inferior leads and one with changes restricted to septal leads, had no ST segment depression in lead CM5. When ST segment shift from the baseline electrocardiogram was measured the magnitude of depression was greatest in lead CM5 in only 63% of the patients. During angioplasty of the left anterior descending coronary artery, lead CM5 showed ST segment depression in seven patients, ST segment elevation in two, and a biphasic response in one. Two of the three patients with balloon inflation in right coronary artery developed ST segment elevation in lead CM5. Thus lead CM5 is a reliable lead for detecting subendocardial ischaemia experienced during everyday activities in anginal patients. During total occlusion of coronary arteries (as in variant angina or myocardial infarction) lead CM5 commonly shows ST segment depression and changes due to right coronary artery occlusion may not be detected.

Bipolar Lead Recording in Ambulatory St Segment Monitoring

Bipolar Lead Recording in Ambulatory St Segment Monitoring

Multiple unipolar lead electrocardiographic monitoring during exercise in severe coronary artery disease: a comparison with bipolar lead monitoring

A system of 21-lead electrocardiography was used to assess 21 patients with severe angina during and after exercise using on-line computerised ST segment analysis. A direct comparison was made between the results obtained from 18 unipolar precordial leads and those from bipolar leads CM5 and CC5. Treadmill exercise was performed 48 hr prior to cardiac catheterization, which revealed luminal narrowing of at least 70% in one or more major coronary arteries in all cases. In all cases the ST depression exceeded 1 mm in both CM5 and CC5 at the peak of exercise. The magnitude of ST depression was greater in the bipolar leads in 75% of cases and in the remaining 25% the greatest peak ST depression occurred in a single unipolar lead. There was no correlation between the magnitude of ST depression and the number of coronary vessels involved. Isopotential surface mapping in the anterior, lateral and inferior projections from the unipolar leads at each stage of exercise failed to show a correlation between the area or distribution of ST segment change and the number or anatomical location of the vessels involved. It was not possible to show that the multiple-lead system could differentiate the site and severity of coronary artery disease in these patients with angina. The multiple-lead system was cumbersome and time-consuming in application and therefore cannot be recommended for routine exercise testing.

Effect of exercise on ventricular response to atrial fibrillation in Wolff-Parkinson-White syndrome.

Ten patients with Wolff-Parkinson-White syndrome underwent cardiac electrophysiological study extended to include the induction of atrial fibrillation at maximum exercise in the upright position. This was performed using a new temporary bipolar lead with a helical active fixation tip for atrial pacing. The highest rate of atrioventricular conduction via the accessory pathway was greater during exercise than at rest in all 10 patients (mean increase 28%). In three cases the resulting ventricular rate exceeded 300 beats/min, but no patient had severe symptoms or ventricular arrhythmias. The exercise induced enhancement of accessory pathway conduction may significantly but unpredictably affect the risk from spontaneous atrial fibrillation especially in patients with coronary artery disease or in those taking antiarrhythmic drugs. The test procedure was sufficiently simple and well tolerated to be included in our routine electrophysiological investigation.

Problems of artificial pacemaker therapy.

Four hundred and sixty-seven cases with implantation of an artificial pacemaker were studied. The postoperative survival rate was 63% for 15 years. Seventy-two percent of type III patients of the sick sinus syndrome were free from postoperative thromboembolism and the lowest of the three types of the sick sinus syndrome. Comparing postoperative physical activity, cardiothoracic ratio and exercise tolerance time, physiological pacing was superior to ventricular pacing in hemodynamic effects and clinical symptoms. In a hundred cases of physiological pacing, complications and problems of physiological pacing were discussed. Atrial sensing failure and over-sensing were observed in seven and two cases respectively. A low amplitude of atrial potential and use of unipolar atrial leads were considered to be the main causes of these complications. Bipolar lead should be used as the atrial lead to avoid such complications, because the atrial potential by bipolar leads is not less than that by unipolar leads. Atrial sensing may be more sensitive without electromagnetic interference. The fixed A-V delay time whenever the atrium is sensed or paced, often results in a ventricular fusion beat and hemodynamic change on every beat, according to the interval of atrial and ventricular contractions. The A-V delay time should be changed in accordance with atrial sensing or pacing.

Simultaneous atrial and ventricular electrogram transmission via a specialized single lead system.

No telemetrically monitorable pacemakers are capable of detecting and transmitting the complete electrogram (EGM) during normal and paced rhythms, although some are capable of detecting and transmitting either the P- or R-wave. A new lead and telemetry-pacemaker system has been developed that permits the transmission of the complete EGM and is not adversely affected by pacemaker outputs or after-potentials. Electrodes are placed in the right ventricle and atrium to optimize EGM detection. These A-V data probe electrodes are electrically separate from the pacing-sensing electrodes but are structurally part of a coaxial ventricular lead that is no larger than a conventional bipolar lead (2.3 mm). The telemetry system is also compatible with telephone monitoring systems. The system has consistently demonstrated its ability to detect accurately the EGM during normal sinus rhythms and does not affect atrial, ventricular, or A-V sequential pacing. In addition, this system can detect and transmit EGM abnormalities, including ectopic beats, retrograde conduction, and ischemic changes. A-V data leads with telemetry monitored VVI pacemakers have been implanted in dogs for over two years. This system will provide the means to detect and telemetrically record noninvasively the entire normal and abnormal EGM, even in pacer dependent patients. (PACE, Vol. 7, November-December, 1984).

Lack of protection against ouabain cardiotoxicity after chronic ablation of the area postrema in cats

We evaluated the hypothesis that the area postrema facilitates the cardiac arrhythmias caused by toxic doses of digitalis. The arrhythmic dose of ouabain was determined in four cats with chronic selective destruction of the area postrema, and in a control group of two sham-operated cats and three normal unoperated cats. The cats were anesthetized with pentobarbital, and polygraph records were made of end-tidal P co 2, arterial blood pressure, heart rate, and the electrocardiogram (lead II and a bipolar lead in the superior vena cava). The vagosympathetic trunks were cut bilaterally, and 1 h later an i.v. infusion of [ 3H]ouabain was begun at the rate of 1.71 nmol/kg/min. This was continued until ventricular tachycardia appeared, as determined electrocardiographically. The total ouabain dosage required for ventricular tachycardia was recorded, and the ouabain concentrations in the arterial plasma and in the myocardium were determined by liquid scintillation counting. No statistically significant difference was found between the chronically postremectomized cats and the controls in any of these measures of ouabain cardiotoxicity. These results indicate that the area postrema plays no important role in the cardiotoxic action of ouabain in pentobarbital-anesthetized, vagotomized cats.

The central venous blood temperature as a guide for rate control in pacemaker therapy.

True physiologic pacing is only feasible in patients with heart block and normal sinus rhythm using atrial synchronized pacing. In sick sinus syndrome (SSS) or atrial fibrillation no adequate sensing possibility is present. For these conditions something other than electrical signals must be found to guide rate control. In clinical experiments a thermistor integrated in a bipolar pacing lead was implanted in one of the authors as well as in a pacemaker patient. Treadmill tests at 3, 6, and 10 km per hour have shown no substantial increase of the central venous temperature (CVT) in the lower effort range; an increase of 0.6-0.75 degrees Celsius (degrees C) in the medium range; and an increase of 1.35 degrees C in the higher range, respectively. External pacing in the author, or rate variations by programming the VVI, M unit in the patient at rest do not influence CVT. CVT correlates well in the medium-range group, which mostly reflects the capabilities of the average pacemaker patient. In the higher effort range a delay between rate increase and increase of CVT is noticed. There is no increase in CVT beyond the physiologic variations in the lower effort range.

Lead Systems: Sensitivity and Specificity

In this article, the modified 12-lead system and the bipolar lead systems are discussed, both of which may provide adequate sensitivity and specificity of stress tests for clinical purposes. A single lead V5 or, preferably, bipolar modification of lead V5 may be adequate in certain situations in which cost or the type of population being tested legitimizes such a choice. However, the modified 12-lead system is far more popular for the diagnosis and follow-up of patients with ischemic heart disease. The final choice of lead system for monitoring stress tests will ultimately depend on the needs and resources of a given laboratory.

Utility of the filtered bipolar esophageal lead in the diagnosis of arrhythmias.

Electrophysiologic study was performed in 25 patients with tachycardia or bradycardia attacks. The coronary sinus (CS) and filtered bipolar esophageal electrograms were recorded simultaneously to compare the phase of atrial activations. During sinus rhythm and high right atrial pacing, the esophageal and proximal CS atrial activations were nearly simultaneous but earlier by 26 +/- 5 msec on the average than the distal CS atrial activations. During reciprocating tachycardia due to reentry using a left-side accessory atrioventricular pathway for retrograde conduction the esophageal and CS atrial activations occurred earlier than the low septal right atrial activation, so the esophageal lead can be used as a substitute for the CS lead to clarify the eccentric retrograde atrial activation sequence. By using the filtered bipolar esophageal lead, the interval from Q wave on the surface electrocardiogram to the first rapid deflection in the esophageal atrial activation (Q-AESO interval) was measured in 15 patients with supra-ventricular tachycardia. All patients with reciprocating tachycardia due to reentry using a left side accessory atrioventricular pathway had Q-AESO intervals between 100 to 130 msec and four of five patients with a right side accessory atrioventricular pathway for retrograde conduction had Q-AESO intervals between 130 to 150 msec. In contrast, all patients with reentry in the atrioventricular node had Q-AESO intervals between 30 to 60 msec. The esophageal lead is also of value in the prompt diagnosis of atrial flutter and ventricular tachycardia, since the esophageal electrograms readily reveal the relationship between atrial and ventricular activations. In conclusion, the filtered bipolar esophageal lead provides a non-invasive method for the quick diagnosis of various arrhythmias.

Thresholds for transesophageal atrial pacing.

To determine the thresholds for transesophageal atrial capture, as well as factors that may influence the thresholds, we measured the minimal current and pulse width required to pace the atria through transesophageal bipolar lead systems in 12 patients, ranging in age from 1 day to 19 years, during 19 episodes of reentrant supraventricular tachycardia. Depending on the patients' age and size several electrode catheters were used. The protocol called for 1-msec step-wise increments in pulse width. At each pulse width the current was increased by 1 mamp until capture was achieved. The mean minimal pulse width and mean minimal current required for capture were 5.8 msec and 13.6 mamp, respectively. Atrial capture was achieved in 75% of attempts at a pulse width and current equal to or less than 6.5 msec and 17.5 mamp, respectively. No correlation between current and pulse width on the one hand and age, height, weight, or body surface area on the other was detected. Likewise neither electrode type nor existence of structural heart disease influenced the threshold required for capture. We conclude that atrial capture can be readily achieved through transesophageal electrodes and is not influenced by the subject's age or size.

Radiographic pseudofracture of the Medtronic bipolar polyurethane pacing lead

with consequent prosthesis-patient mismatch3; in fact, the prosthetic aortic valve index at operation, calculated retrospectively, was 1.5 cm2/m2. Significant transaortic systolic gradients have been reported postoperatively with small-sized Hancock xenografts.’ In the present case stenosis was made worse by fibrous tissue overgrowth on the cusps, which is observed mainly on the mitral porcine prostheses,’ and by central impingement of the valve prongs. The latter has recently been recognized as a cause of hemolysis5 and thrombus formation: both of which were absent in our case. Currently, concern exists that the standard orifice Hancock valve may not be a suitable substitute for the native aortic valve in the presence of a narrowed anulus if surgical enlargement of the latter is not performed.7 The case herein reported provides evidence that the already unfavorable ratio of internal to external diameter of small-sized Hancock valves may be worsened, even in the absence of structural changes of the cusps, by fibrous tissue overgrowth and inward bending of the struts, an association previously unreported.

Clinical evaluation of the internal automatic cardioverter-defibrillator in survivors of sudden cardiac death

An R-wave synchronous implantable automatic cardioverter-defibrillator (IACD) was evaluated in 12 patients with repeated episodes of cardiac arrest who remained refractory to medical and surgical therapy. Seven men and 5 women, average age 61 years, surgically received a complete IACD system. Coronary artery disease was found in 11 and the prolonged Q-T syndrome in 1. The average ejection fraction was 34%, and 6 patients had severe congestive heart failure (New York Heart Association class III or IV). The IACD is a completely implantable unit consisting of 2 bipolar lead systems. One system uses a lead in the superior vena cava and on the left ventricular apex through which the cardioverting pulse is delivered. The second system employs a close bipolar lead implanted in the ventricle for sensing rate. After the onset of ventricular tachycardia or fibrillation, the IACD automatically delivers approximately 25 J. Postoperative electrophysiologic study in 10 and spontaneous ventricular tachycardia in 1 patient demonstrated appropriate IACD function and successful conversion in all with an average of 18 ± 4 seconds. The induced arrhythmias were ventricular tachycardia (160 to 300 beats/min) in 9 and ventricular fibrillation in 1. These data demonstrate that ventricular tachycardia, not ventricular fibrillation, was the predominant rhythm induced during programmed ventricular stimulation in these survivors of cardiac arrest and that the IACD effectively responded to a wide range of ventricular tachycardia rates as well as ventricular fibrillation. Use of the IACD offers an effective means of therapy for some patients who otherwise may not have survived.

Effect of exercise on QRS duration in healthy men: a computer ECG analysis.

Increased sympathetic tone with exercise enhances ventricular conduction and would be predicted to shorten QRS duration. Previous studies, however, have not consistently documented such changes. Using a digital electrocardiograph (ECG) cart sampling at 500 Hz, a bipolar precordial lead (V5-V2) was recorded (supine, at end expiration) in 25 healthy men (mean age 29 yr, range 19-37) at rest and immediately after submaximal treadmill exercise. QRS duration was measured on complexes recorded at high gain and expanded time scale. A significant (P less than 0.0005) decrease [4.9 +/- 2.3 (SD) ms] in QRS duration was noted, and decreased QRS duration was observed in all 25 subjects (range 1-10 ms). Furthermore there was significant (P less than 0.01) shortening of the intervals between QRS onset and Q-wave nadir (1.2 +/- 2.0 ms) and between QRS onset and R-wave peak (2.4 +/- 2.5 ms), as well as of the Q-R interval (1.3 +/- 2.7 ms). However, there were no significant differences in percent shortening of early vs. later phases of the QRS. To exclude digital sampling errors the same protocol was also applied in 11 healthy men by using an analog ECG cart. QRS duration immediately postexercise shortened by 7.1 +/- 4.3 ms (range 2-11.5 ms), which was not significantly different from the results obtained with the digital ECG. We conclude that decreased QRS duration is a physiological response to moderate treadmill exercise in healthy men, reflecting enhancement of conduction in early, middle, and later phases of ventricular activation.