An analysis of electrocardiographic, radiographic, and vectorcardiographic findings in patients with implanted cardiac pacemakers

Clinical

communications

An analysis of electrocardiographic, radiographic, and vectorcardiographic in patients with implanted cardiac

T. K. P. W. R. M. W. H.

findings pacemakers

Kaul* Macfarlane Thomson Bain

Glasgow, Scotland

Electrocardiography and lateral chest radiographs are normally used to locate the site of implanted electrodes of cardiac pacing systems.’ Faults in the latter can be detected by routine bipolar lead electrocardiography,’ but malpositioning of the implanted electrodes is more difficult to determine. The morphology of QRS complexes in a 12-lead ECG is a valuable but not an infallible guide to the site of stimulation,” while interpretation of lateral chest radiographs also has limitations.’ Vectorcardiograms have also been reported as being of use in the study of both the pacing system5 and the intracardiac conduction system,6.7 but little attention seems to have been paid to the pacemaker artefact stimulus and to early ventricular depolarization vectors in the detection of electrode placement errors. The present study was undertaken to determine whether the following three techniques would in combination provide a reliable indication of electrode placement errors and their site of implantation: 1. Pacemaker artefact vectors as determined from the three orthogonal-lead ECG (and hence the vectorcardiogram) 2. QRS morphology from three orthogonallead and I2-lead ECGs, and 3. Chest radiographs.

From the Cardiology,

University Royal

Departments of Cardiac Infirmary, Glasgow, Scotland.

Received

for publication

June

Accepted

for publication

Oct. 25, 1979.

Reprint Royal *Present

686

requests: Infirmary, address:

June,

and

Medical

12, 1979.

Mr. W. H. Bain, University Glasgow G4 OSF, Scotland. Broadgreen

Surgery

Hospital,

Dept.

Liverpool,

1980, Vol. 99, No. 6

of Cardiac England.

Surgery,

Patients

and methods

Serial 12-lead ECGs and chest radiographs (lateral and posteroanterior views) of 300 consecutive patients were recorded and studied after the implantation of permanent pacemakers. The nature of any preoperative conduction defect, and site of myocardial infarction in relevant cases were also considered. Two hundred and ninetyseven patients received transvenous and three had epicardial systems. The age range of patients in this group was 33 to 94 years, while individual recordings were made at any time between 1 day and 8 years after the implantation. Vectorcardiograms derived from the modified axial three orthogonal-lead system,x were recorded in all patients who presented with abnormal x-ray appearances or an abnormal ECG-i.e., not type A or B (see below)-while a sample of patients with a normal 12-lead ECG and x-rays also had vectorcardiograms analyzed. The 12-lead ECGs were classified into eight different groups as follows: Type A: LBBB with LAD and tall R in Leads v,, vs Type B: LBBB with LAD and dominant S in Leads V,, V, Type C: LBBB with LAD; R > 0.2 mV. in Leads V, or V? or V, Type D: IVCD with extreme LAD and dominant S in Leads V,-V, Type E: RBBB with RAD Type F: Probable bilateral bundle branch block with LAD Type G: RBBB with extreme left axis deviation Type H: Sinus rhythm.

0002.8703/80/060686

+ 08$00.80/O

0 1980

The

C. V. Mosby

Co

Findings in patients with implanted pacemakers

Table I. 12-lead ECG patterns

endocardial,

and site of implantation

of A B C

D E F

G H

145

RV outflow tract

74

8

2

117

17

5

6

12

2

2

-

1

-

1

27

-

11

1

-

-

4 2

3 -

-

1

3

-

-

_-

L.B.B.B

= left

Posterior

1

-

3 -

34

3%

3 bundle

branch

The single channel electrocardiograph used to record the 12-lead ECG had a low frequency response (flat to under 50 Hz). The three-lead ECGs were recorded with amplifiers having a response flat to 200 Hz and were written out on an Elema 34 ink jet writer with a superior response. While each of these frequency responses is inadequate for exact measurement of pacemaker stimulus amplitude, they are sufficient to determine the polarity of the stimulus in each lead. An approximate direction of the stimulus vector can thus be inferred. This vector was classified as being directed superiorly (S) or inferiorly (I), posteriorly (P) or anteriorly (A), and to the right (R) or left (L). The mean spread of ventricular excitation up to approximately 20 msec. after QRS onset was also determined from the three-lead ECG and was described in similar terms. Vectorcardiographic loops were plotted on a PDPSE computer after analogue to digital conversion of the ECG signals. A typical complex was selected for display. X-rays were used to determine whether the pacing catheter was pointing anteriorly or otherwise-i.e., a line joining proximal to the distal electrode would point anteriorly in the lateral x-ray of a normally implanted electrode catheter.

American Heart Journal

R V body

34

Totals: ventricle;

RV apex

-

84

L.B.B.B. with LAD and tall R in V,-V, L.B.B.B. with LAD and dominant S in V,-V,, L.B.B.B. with LAD and R < 0.2mV. in V,, VI, or v, I.V.C.D. with R.A.D. and dominant S in V,-V, R.A.D. & R.B.B.B. Probable bilateral bundle branch block with L.A.D. R.B.B.B. and extreme left axis deviation Sinus rhythm

RV = right axis deviation.

Epicardium

patients

ECG patterns

Abbreviations: RAD = right

(297

Position of pacing electrode in lateral x-ray

Number

Type

of pacing electrodes in 300 patients

3 epicardial)

236 block;

R.B.B.B

--ii-

38 = right

bundle

branch

block;

LAD

-z = left

axis

deviation;

Results

The 12-lead ECG patterns and radiological appearances of the implanted pacemakers in the 300 patients are summarized in Table I. Two hundred twenty-nine of these patients had a “normal” LBBB pattern (76.3%); type A was found in 84 (28’%), and type B was found in 145 patients (48.3%). “Abnormal” type C LBBB (with LAD and a prominent R wave in Leads V,, V,, or V,) was found in 27 patients (9%). In this group the catheter electrode pointed essentially retrosternally or towards the RV base in all but two patients in whom it was directed posteriorly (Table I). The other ECG patterns, types D to G, were found in only 10 patients. The catheter electrode system was directed retrosternally in 95% of patients, although the catheter tip was in the RV body in 38 (12.7%) or in the outflow tract of the ,right ventricle in 9 patients (3%). The normal pattern of the stimulus artefact was SPR, in agreement with the findings of others,G although a number of patients with a normal QRS morphology and x-ray appearance had an SAR pattern of stimulus artefact together with IPL or SAL initial excitation patterns, the important point being a leftward ventricular depolarization. Some patients were difficult to

687

et

Kaul

al.

II. Unusual ECG and x-ray findings and the QRS vectors in 17 patients

Table

Number

of patients

1

2 3

4 5 6 7 8 9

10 11 12 13 14 15 16 17

Position of electrode in lateral x-ray

ECG pattern

Pi-e-operaticv conduction defect

SAR P SAR SPR SAR SAR

Posterior Posterior Posterior Posterior Posterior

B B B B B

Sick sinus MI, CHB CHB CHB CHB

Posterior Posterior Posterior Posterior Posterior

C C B D G

SPR SPR SPR SPL IAR

Posterior Posterior Posterior

CHB Sick sinus Sick sinus 2:l AV block L post-hemiblock MI CHB CHB CHB

Posterior Anterior Anterior Anterior

2:l RBBB CHB CHB CHB

SPL SPL IPR IPR

RV = right ventricle; Key to ECG patterns

MI = myocardial infarction; as in Table I. Key to pacing

IAR SPR SPR

MI

CHB = complete heart block; stimulus and Cardiac Excitation

type in that the stimulus artefact was generally large and biphasic. In cases of doubt, the initial component of the stimulus was chosen as indicative of the stimulus direction. The normal pattern of early ventricular depolarization with RV stimulation was mainly SPL. This is in agreement with the findings of Zoneraich and colleagues,’ but at slight variance with the findings of Castellanos and co-workers,fi who referred to the “initial delay” of the stimulus artefact rather than to early ventricular depolarization. In their series of patients with transvenous pacing, it would appear that 80% had biphasic stimulus artefact, which was not the case in our series. In all but 17 patients the ECG, x-ray, and stimulus vector agreed on the normal or abnormal position of the pacemaker electrodes. The details of these 17 patients are presented in Table II. In 14 patients (4.7 o/o),the pacing electrode system was directed posteriorly, and the ECG pattern was either B,C,D,E,F, or G. The initial propagation of excitation in these 14 patients is outlined in Table II, which also summarizes the stimulus artefact vectors. This table also includes three other patients with an unusual combination of ECG, VCG, and x-ray findings. Each of them had a perforated right ventricle. 688

Pacing stimulus

In&in1 cardiac excitation

Site implantation

SPL

RV

IPL SPL SPL SPL I&L

RV RV RV RV

IPPL SPL SPR SPR SPR SPR SPR SAR &R IPR SPR

Coronary Coronary

RV RV RV venous venous

system system

Coronary Coronary Coronary

venous venous venous

system system system

Coronary Perforation Perforation Perforation

venous RV RV RV

system

AV = atrioventricular. as described in text.

Discussion

Although the pattern of “normal” LBBB occurred in 229 patients (76.3%), the catheter electrode was anterior in 233 and posterior in six, the latter group all having type B pattern. Stimulation of the basal portion of the right ventricle” will generate an LBBB pattern with base to apex excitation, while the electrical axis will point to the left and inferiorly either on account of (a) an endocardial electrode falling short of the apical position in RV, or (b) an electrode bent against the septum, or (c) epicardial leads implanted at the base of the RV. Since the electrode system normally lies in an anterior position-i.e., a line from the proximal to the distal electrode points anteriorly, the 223 out of 229 patients with type A or B ECG were regarded as having the pacing system in the RV apex. The six out of 229 patients with a posteriorly directed catheter system were considered as possibly having the electrodes in the coronary venous system.4 This point will be discussed below. In the 27 patients with type C ECG, the pacing electrode system was directed anteriorly in 25 and posteriorly in two. The initial QRS activation was directed to the left, posteriorly and superiorly in all but three of 27 patients in whom the initial QRS vector was directed to the right, posteriorly, June,

1980, Vol. 99, No. 6

Findings in patients with implanted pacemakers

and superiorly (Fig. 1). These three patients also presented with exit block and an early penetration of myocardium occurred as indicated by intermittent diaphragmatic twitching (patient No. 15, Table II), presence of sanguinous effusion, and clots within the pericardium (patients No. 16 and 17, Table II), and resistance encountered when the catheter electrodes were dislodged at the implantation of a new epicardial electrode system. It might be postulated that the variation in the QRS pattern in the precordial leads in Types A, B, and C is due to differing relationships of the left and right ventricles and the anteriorly placed stimulating electrode. Despite the widespread use of per-venous RV pacing, occurrence of an RBBB pattern during RV pacing is an infrequent finding. The explanations suggested for this finding are (a) perforation or an early penetration of RV, (b) retrograde conduction of the excitation wave through the conduction system of the heart,g (c) spread of impulses across the Purkinje bridge between the left and right-sided conducting systems at the apex, (d) high position of the electrode stimulating the mid-septum which is usually thin and may, therefore, depolarize the LV first, or (e) RV activation delay due to disease of the conducting system of the right ventricle.‘0 According to SodiPallares and Calder’s” concept of septal anatomy, similar QRS patterns can be obtained after the stimulation of the apex of the heart at either side of the interventricular septum. The electrical stimulation of left ventricle (by an epicardial lead or an endocardial electrode misplaced into the coronary venous system [Fig. 21 or by an endocardial electrode which has perforated the myocardium) provides a classical RBBB pattern.“’ However, the QRS complexes and pattern of excitation may vary with the exact site of LV stimulated.” The electrical axis is orientated to the right and inferior by with superior implantation. If the electrode is adjacent to the apex and situated (though not orientated) anteriorly, the general excitation will occur to the right, posteriorly, and superiorly due to the spread of excitation in the RV being dominant, producing S waves from Leads V, to V, in the ECG (Case 9, Table II). A more anterior position will yield an initial R wave in both Leads V, and V,, while a slight posterior deviation produces a negative deflection in Lead V, but still with an R wave in Lead V,. American Heart Journal

AL

AF

VI

v2

BH v3

v4

fli!Fbd VS

V6

,:’:

,,..,”., ‘,.. ..:..

.*’

RS Fig. 1. The initial ventricular excitation is to the right posteriorly and superiorly in a patient with type C ECG pattern; the catheter electrode was directed to the anterior.

With the stimulation of the posterobasal portion of LV, the activation may proceed through the septum as well as laterally and superiorly. This produces LAD and the net effect in the transverse plane is a resultant anteriorly directed QRS vector, giving a tall R wave in Lead V, with diminishing R waves on either side-i.e., to Leads V, and V, respectively. A bipolar pacing system is an ideal model of an electrical dipole with a source and sink for electrical current, which should flow directly from one electrode to the other during activation of the system. Thus if the direction of the stimulus current is measured using an orthogonal lead system, the approximate orientation of the electrode system can be determined electrocardiographically. For example, in the normal situation, an electrode system will lie in the apex of the RV pointing anteriorly with the proximal electrode superiorly positioned with respect to the distal electrode. The stimulus “vector” will then be orientated along a line from the distal to the 689

Kaul et al.

oVF

Fig.

2. Lateral

chest

x-ray:

the electrode

system

is orientated

vb

posteriorly.

The

ECG

shows

LAD,

RBBB

(Type

G).

proximal electrode, and normally will therefore be directed superiorly, posteriorly, and generally to the right side of the patient-i.e., at about 10 o’clock, as seen from the front, above, and also as seen from the right (i.e., right sagittal view). A normal stimulus vector is therefore described as SPR. If the electrode system is directed posteriorly (Fig. 2), an anteriorly directed stimulus vector would be expected. This was not always found and it is suspected that at the time of operation the connection to the generator was reversed to produce an expected negative deflection of the stimulus artefact in Leads I, II, and III. With respect to early ventricular depolarization, the pattern noted in the normal was SPL. With RV apical stimulation, it appeared that in the typical normal, the resultant ventricular depolarization was directed superiorly to the left, presumably being due to the net effect of septal and LV free wall excitation in an apex-base direction. The posterior position of transvenous endocardial electrodes in a lateral chest x-ray, as found in 14 patients (Table II) has been considered diagnostic of malpositioned electrodes in the coronary venous system.‘. I2 However, interpretation of the lateral chest x-ray alone can be misleading.” In eight patients in the present series, although the

690

catheter electrode was directed posteriorly (Table II), the 12-lead ECG patterns (B or C) together with the stimulus (SAR or SPR) and excitation (SPL or IPL) vectors suggest that the pacing electrode was in the RV (Fig. 3, A and B). In the remaining six patients, x-ray, ECG, and vector findings were unequivocally suggestive of malpositioning of the electrode in the coronary venous system (ECG pattern D, E, F, G, and initial excitation SPR) (Table II). In all but three patients with malpositioned electrodes (patients No. 7, 8, and 14, Table II) intermittent failure of pacing occurred and resiting of the electrodes was necessary. After minimal displacement, it was possible to advance the malpositioned electrode in the right ventricle into the main pulmonary artery at remanipulation. The malpositioned electrodes in the coronary sinus had to be passed through the tricuspid valve at the reimplantation. At each subsequent repositioning a satisfactory implantation of the electrodes into the right ventricular apex was confirmed with the help of a lateral chest x-ray and vectorcardiogram. An overzealous attempt to implant the catheter electrode into the RV apex in the frontal projection may result in bending of the catheter electrode tip against the septum or the floor of the RV. With such a malpositioned RV electrode,

June,

1980, Vol. 99, No. 6

Findings

in patients

with implanted

pacemakers

VF

Fig. B).

3A.

Lateral

x-ray;

the electrode

system

is orientated

posteriorly.

The

ECG

:

Journal

(Type

:

i 4’. ?.. : ‘a

i>,J

‘4. .,

Heart

and LBBB

F

Conclusions

The interpretation of the morphology of the 12-lead ECG and appearances of the lateral chest radiographs are valuable but not an infallible guide to the site of implantation of the pacemaker electrodes. A simple analysis of stimulus artefact

LAD

,..‘.. . ..~.

the pacing may be intermittent due to the instability of the electrodes; and in a lateral x-ray it could point posteriorly, but the excitation pattern as determined with the ECG and vectorcardiogram would indicate RV stimulation. Thus, although such a malpositioned electrode in the RV may present identical to an electrode placed into the coronary venous system clinically and radiologically, it can be correctly diagnosed by studying the excitation pattern with 12-lead ECG and vectorcardiogram. The findings can be summarized as in Fig. 4, where a diagnostic tree is presented. From this it can be seen that the VCG findings are of value in a limited number of patients. If a strict procedure for connection of the pacemaker electrode were to be followed, the posterior or anterior orientation of the electrode catheter with the help of pacemaker stimulus artefact could be inferred even in the absence of a lateral chest radiograph.

American

shows

Fig. 38. ventricular 1Y.

QRS vector excitation

T

R.S.

of the same patient as in is to the left, posteriorly,

Fig. 3A. Initial and superior-

691

Kaul

et al.

QRIENTATION !E PACEJ4AKER

INITIAL !(j@iE* DEFOLARISATION

gAGNoSIS

YES

CORONARY VENOUS SYSTEM Fig. 4. A diagnostic encloses a descriptive

tree for ‘locating statement.

the pacemaker

and initial ventricular activation vectors in cornbination with 12-lead ECG and lateral chest radiographs has proved useful in diagnosing the electrode malplacement errors in the postimplantation period or at the time of implantation. Summary

In patients with implanted cardiac pacemakers, the radiological appearances, and the configuration of the 12-lead ECG have been conventionally used both to locate the site of the electrode implantation and to diagnose electrode placement errors. These techniques have limitations, and in the present study vectorcardiographic data derived from the pacemaker stimulus and the spread of ventricular depolarization has been added to improve accuracy. Three hundred patients with implanted cardiac pacemakers were studied. Unusual QRS complexes as determined from the 12-lead ECG were found in 37 (12%) and the position of the pacemaker electrodes determined from the lateral chest x-ray was outside normal (R.V. apex) in 61 patients (20.3%). A combined interpretation of the ECG, chest x-ray,

692

electrodes.

A diamond encloses

a question,

while

a

circle

and the vectorcardiogram agreed on positioning (correct or incorrect) in all but 17 patients (5.6%). Three patients had a perforated right ventricle, while further study of the other 14 suggested malpositioning of the catheter electrode in the right ventricle or in the coronary venous system. An analysis of the ECG patterns, x-ray appearances, and vectorcardiograms is presented with respect to the diagnosis of pacemaker electrode placement errors and a logical tree for establishing the position of the pacemaker is introduced. The authors are grateful to Mr. F. M. Towler and Miss Jean McDonald of the Medical Illustration and Photography Section of the University Department of Surgery, Royal Infirmary, Glasgow, and to Miss P. Robinson for their help in the preparation of the manuscript. REFERENCES 1.

2.

3. 4.

Meyer, J. A., and Miller, K.: Malplacement of pacemaker catheters in coronary sinus, J. Thorac. Cardiovasc. Surg. 57:511, 1969. Thomas, D. L., and Green, D. G.: Improvements in the technique of assessing implanted cardiac pacemakers, Med. Biol. Engineering 12589, 1974. Castellanos, A.: Unusual QRS complexes produced by pacemaker stimuli, AM. HEART J. 77:732, 1969. Kaul, T. K., and Bain, W. H.: Radiological appearances

June, 1980, Vol. 99, No. 6

Findings

5.

6.

7.

8.

of implanted transvenous endocardial pacing electrodes, Chest 72:323, 1977. Macfarlane, P. W., and Green G. D.: Vectorcardiographic studies of implanted cardiac pacemaker stimuli, Annals of the Medical Section of the Polish Academy of Sciences 16:345, 1971. Castellanos, A,, Lemberg, L., Salhanick, L., and Berkovim, B.: Pacemaker vectorcardiography, AM. HEARTJ. 75:6, 1968. Zoneraich, O., Zoneraich, E., and Douglas, A. H.: The vectorcardiographic findings in patients with artificial pacemakers, Dis. Chest 53:436, 1968. Macfarlane, P. W.: A modified axial lead system for orthogonal lead electrocardiography, Cardiovasc. Res. 3510, 1969.

Information

9.

10.

11. 12.

in patients

with implanted

pacemakers

Mower, M. M., Arange, 0. E., and Tobatznik, B.: Unusual patterns of conduction produced by pacemaker stimuli, AM. HEARTJ. 74:24,1967. Barold, S. S., Narula, 0. S., Javier, R. P., Linhart, J. W., Lister, J. W., and Samet, P.: Significance of right bundle branch block patterns during pervenous ventricular pacing, Br. Heart J. 31:285, 1969. Sodi-Pallares, D., and Calder, R. M.: New bases of electrocardiography, London, 19.56, H. Kimpton. Ragaza, E. P., and Shapiro, R.: Radiological recognition of unusual sites of a transvenous catheter pacemaker, J. Can. Assoc. Radiol. 21:214, 1970.

for authors

I

Most of the provisions of the Copyright Act of 1976 became effective on January 1,1978. Therefore, all manuscripts must be accompanied by the following written statement, signed by one author: “The undersigned author transfers all copyright ownership of the manuscript (title of article) to The C. V. Mosby Company in the event the work is published. The undersigned author warrants that the article is original, is not under consideration by another journal, and has not been previously published. I sign for and accept responsibility for releasing this material on behalf of any and all co-authors.” Authors will be consulted, when possible, regarding republication of their material.

American

Heart

Journal

693