Journal of Postgraduate Medicine Medknow Publications and Staff Society of Seth GS Medical College and KEM Hospital, Mumbai, India ISSN: 0022-3859 EISSN: 0972-2823 Vol. 51, Num. 2, 2005, pp. 92-97

Journal of Postgraduate Medicine, Vol. 51, No. 2, April-June, 2005, pp. 92-97

Original Article

Routine chest radiography after permanent pacemaker implantation: Is it necessary?

Edwards N.C., Varma M., Pitcher D.W.

Department of Cardiology, Worcestershire Royal Hospital, Warwickshire

Correspondence Address: Department of Cardiology, Worcestershire Royal Hospital, Warwickshire, Email: nickyedwards@doctors.org.uk

Date of Submission: 27-Nov-2004
Date of Decision: 21-Mar-2005
Date of Acceptance: 10-May-2005

Code Number: jp05035

ABSTRACT

Keywords: Chest radiographs, pacemaker, pneumothorax

In the late 1980s, concerns were raised about the provision and low rate of permanent pacing in the UK. In 1990, the UK implanted around 140 implants/million/year, which was only 27-41% the rate of other European nations.[1] To meet the needs of an ever-aging UK population, expansion was necessary and was primarily channelled through the district general hospitals setting (DGH). Twenty years on, and with ever increasing targets (implantation of new systems was set at 450 per million in 2002), DGHs have repeatedly been shown to provide convenient, safe and effective pacemaker services and hence now shoulder much of the pacing burden. Today over 180 centres are involved in pacemaker implantation and in 2000, implantation of new systems exceeded 23,000 in the UK and Ireland.[2]

Advances in pacing technology and techniques have made this a highly cost-effective and relatively safe procedure.[3] Virtually all pacing systems are implanted transvenously under local anaesthesia, using either the cephalic vein by cut down or direct puncture of the subclavian vein. The subclavian route, particularly with more inexperienced operators, is associated with a higher risk of procedural complications such as pneumothorax, arterial puncture, and wound haematoma. However, in experienced hands, the incidence of such problems is low. In addition, this route is quicker, requires less surgical expertise and facilitates insertion of more than one pacing lead.[4]

Elective pacing is performed as a day-case procedure in our unit and elsewhere. Traditionally, it has been standard protocol to assess lead position at the time of implantation using fluoroscopy, followed by postero-anterior (PA) and lateral chest radiographs immediately after pacemaker insertion.[5] The purpose of these radiographs is firstly to exclude pneumothorax in patients who have had direct subclavian puncture and secondly to record the position of the pacing leads and provide a comparison for future reference in case of pacing problems.[6],[7]

We questioned the usefulness of routine chest radiography after pacemaker implantation. In the presence of an uncomplicated procedure and satisfactory pacing and sensing parameters, does it really add information that will change the clinical management?

MATERIALS AND METHODS

1. Type of pacing system or revised system implanted.
2. The actual number of patients undergoing post-procedural PA and / or lateral chest X-rays after pacemaker implantation.
3. The adequacy of pacing lead contours and electrode position.
4. The presence of pneumothorax

RESULTS

In the 15-month study period, 126 consecutive elective day-case patients were paced. One hundred and sixteen patients had implantation of new pacemaker systems (single or dual chamber) and 10 patients had system revisions (8 were upgraded from single to dual systems and 2 had new atrial and ventricular leads inserted).

Dual chamber systems (DDD) were implanted in 91 (72%) patients. Thirty-five patients (28%) had single chamber systems of which 30 (86%) were ventricular (VVI) and 5 (14%) were atrial (AAI).

Post-procedural PA chest radiograph was performed in 123/126 patients (98%). Three patients (2%) did not have a PA X-ray. Post-procedural lateral radiograph was performed in 69/126 (55%) patients only. In total, 60 patients (3 without PA and 57 without lateral x-rays) had only single view radiography immediately after pacing. One patient failed to have any post-procedural chest radiography. None of this patient group had any immediate or subsequent complications during pacemaker follow-up. The reasons for incomplete post-procedural radiographic studies were not established.

In the patients who underwent PA radiographs, the ventricular lead was visualised and considered correctly positioned in 86% for VVI and 96% for DDD systems. In the lateral view, the ventricular lead was deemed correct for 82% for VVI and 90% for DDD [Table - 1] and [Table - 2].

The atrial lead was considered correctly positioned in all five patients with AAI systems who underwent PA and lateral views. The atrial lead in DDD systems was judged correct in 91% on PA and 94% on the lateral view [Table - 2] and [Table - 3].

In total 192 post-procedural CXRs were performed. In 27 radiographs (14%) (16 PA and 11 lateral) either the ventricular, atrial or both leads were considered radiographically sub-optimal for lead contour and electrode position. All patients with these "abnormal" CXRs had satisfactory pacing parameters at follow-up pacing checks and did not report adverse symptoms. None required re-operation for lead re-positioning or further chest radiography for pacing-related problems.

Further chest radiographs were recorded for 16 patients from our series. We were able to access the medical notes and review the X-rays of 15 patients in this group [Table - 4].

Three patients required further CXRs for pacing malfunction as the primary indication. All three patients had dual chamber systems and required single lead repositioning (one atrial and two ventricular). Two patients were identified by unsatisfactory pacing parameters during a pacing check immediately after implantation. One patient had failure of atrial sensing and the other had failure of ventricular pacing and sensing. Both underwent successful lead re-positioning. The third patient presented with pre-syncopal episodes two weeks after implant. A pacing check demonstrated intermittent failure of ventricular capture. The ventricular lead was repositioned but still showed poor capture and was replaced successfully with a new lead.

All three patients had post-implantation PA and lateral chest X-rays in which lead positions were considered radiographically correct. Further CXRs performed prior to re-operation were similar to previous CXRs and still had apparently appropriate lead positioning.

Ten patients had subsequent chest X-rays for medical indications unrelated to their pacing systems. Pacemaker follow-up checks have all been satisfactory in this patient group.
Pneumothorax occurred in one patient during implantation of a dual pacing system, an incidence of 0.8% for our series. The diagnosis of pneumothorax was not in doubt as air had been aspirated during the process of achieving subclavian vein cannulation and the patient had developed pleuritic pain. PA chest X-ray confirmed this complication. An intercostal drain was inserted resulting in lung re-expansion and an uncomplicated recovery.

DISCUSSION

The results from this study provide further evidence that district general hospitals can provide a local, safe and effective day-case permanent pacemaker service. [10],[11],[12]

The purpose of this present analysis was to evaluate the need for continued routine chest radiography after pacemaker implantation. The role of routine radiography after pacemaker insertion is not clearly defined. In a Medline search, we identified only a single paper by Grier et al published in 1990[13] supporting a role for chest radiography. In this study, two radiologists retrospectively reviewed chest X-rays of 600 patients who had undergone pacemaker implantation. They identified radiographic abnormalities on CXRs of 131 patients (21.8%). Individual radiographic complications ranged from lung atelectasis (0.3%) to unsatisfactory lead position (5.5%). Despite this high number of radiographic abnormalities, only a few were clinically significant abnormalities which required intervention at that time or later in the clinical course. A total of 60(10%) patients were considered to have either electrode tip malposition or loop abnormalities on their original chest X-rays. However, only three (0.5%) patients required lead repositioning because of pacing abnormalities.

In our case series, only 192 radiographs were performed in total after pacemaker implantation despite our hospital protocol for both PA and lateral views. Twenty-seven (14%) films were considered radiographically sub-optimal for pacing lead positioning after the procedure. However, all had satisfactory pacing parameters at the time of implantation, on subsequent interrogation and had no symptoms, so did not require further intervention. This view is supported by recent work published by Hildick-Smith et al , who reported no benefit from atrial lead repositioning in patients with satisfactory pacing parameters.[14]

We have shown that pacing characteristics are the best means of identifying problems with pacemaker lead position. Post-procedural chest radiographs performed in our series did not influence further management. But do these initial radiographs serve a purpose for later comparison of lead positions? Sixteen patients (13%) from our series underwent further chest radiography at varying dates after pacemaker insertion. Five patients had X-rays for pacemaker-related indications. One patient had radiography to confirm lung re-expansion following iatrogenic pneumothorax. One patient had additional radiography following treatment for a wound infection. Three patients had radiography prior to and after lead re-positioning for pacing system malfunction. All three had PA and lateral radiographs after pacemaker implantation and repeat films prior to lead re-positioning, in which pacing lead positions appeared radiographically correct. Clearly, the need for exploration of a pacing system and possible lead re-positioning is determined by unsatisfactory function of the pacing system and not by X-ray appearances.

The percentage figure for lead re-positioning in our study is similar to that in other studies.[3] However, the number of dual chamber system implants (72%) was higher in our study compared to published national figures (53.7% in 2000).[2] These systems are associated with higher re-positioning and complication rates,[3],[15],[16] emphasising that our lead displacement rate is acceptably low.

An undisputed indication for chest radiography after pacemaker insertion is to confirm the presence of clinically significant pneumothorax. Chest radiography will in this situation guide subsequent management, in terms of the decision to observe, aspirate or insert an intercostal drain. As we have demonstrated, the incidence of pneumothorax is low, less than 1% in our series of 126 patients. All patients had direct subclavian puncture and 75% of the procedures were performed by trainees who had performed less than 50 implants each. In our series, in the single case of pneumothorax, the operator thought a diagnosis of pneumothorax is very likely as air was aspirated at the time of subclavian puncture and the patient developed pleuritic pain. When pneumothorax is suspected or where there is unexplained clinical deterioration, it is clearly important that the patient has immediate chest radiography and other necessary investigations to define the cause.

But what about uncomplicated procedures where the subclavian vein is punctured at first pass or after use of the cephalic vein approach? In such cases, there is no realistic likelihood of pneumothorax. A limitation of this study is that we did not prospectively grade clinical suspicion as to the likelihood of an iatrogenic pneumothorax at the time of pacemaker insertion or the degree of difficulty experienced in obtaining subclavian vein access. It might be argued that chest radiography should be performed in patients in whom subclavian vein puncture proved difficult. This more selective approach may identify patients with clinically silent pneumothorax and guide the need for subsequent CXRs and continued observation. However, investigators have shown that clinically asymptomatic pneumothorax may be of little importance.[3],[13] Grier et al identified 15 pneumothorax in their cohort of 600 patients, yet only one required intervention. This same question has been posed following other procedures such as thoracocentesis, in which pnuemothorax is a recognised complication. Investigators have shown that in symptom-free patients, the risk of developing pneumothorax with clinical consequences was so low that the practice of routine chest X-ray may not be justified. A more selective approach to post-pacing chest radiography may be supported, as has been suggested following thoracocentesis.[17],[18],[19]

Given the results of this study, we are now prospectively collecting data on patients attending for elective new pacemaker implantation. Standard patient demographics, operator, route of implant and pacing data is recorded. In addition, the operator records the degree of difficulty in achieving venous access and performing the implant. We perform post-procedural chest radiographs only in patients with moderate to high likelihood of pneumothorax. We believe the radiological diagnosis of clinically significant pneumothorax will correlate with the operators′clinical suspicion. We believe these selection criteria will be safe, will prevent patients undergoing further radiation exposure through unnecessary CXRs and improve speed of access for other patients requiring radiography.

CONCLUSION

Insertion of permanent pacemaker by experienced operators carries a low risk of complications. We have demonstrated that the key factors which dictate the need for further operative intervention are patient′s symptoms and pacing characteristics. The appearance of pacemaker lead position on chest radiographs performed after implantation does not influence the subsequent clinical course.

Our study suggests that routine chest radiography is not necessary after an uncomplicated pacing procedure with satisfactory pacing parameters and a clinically low probability of iatrogenic pneumothorax.

REFERENCES

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