Patients with a cardiac pacemaker [1–3] or an automatic implantable cardioverter defibrillator  have undergone extracorporeal shock wave lithotripsy (ESWL) for renal calculi without complications. Until a few years ago, pacemaker patients were excluded from ESWL treatment. Instructions for using ESWL recommend precautions with high cardiac risk patients, indeed for patients with 2nd or 3rd degree atrioventricular heart block spark gap generator treatments are still contraindicated. We are not aware of any other reported case and therefore report the case of a patient with complete atrioventricular heart block (CAVHB) who successfully underwent ESWL (Sonolith 3000™ Technomed, France) without an implanted cardiac pacemaker.
A 46-year-old woman was admitted for lithotripsy of two right renal stones. The patient's past medical history and physical examination were unremarkable. Pre-operative laboratory results including electrolytes, were normal. The athletic patient denied having any cardiac symptoms. The pre-operative electrocardiogram revealed a previously unknown complete heart block with a normal QRS complexe. In 1966 an ECG was repeatedly normal. The cardiological assessment consisted of an exercise test (resting heart rate: 50 beats min−1; exercise ventricular rhythm: 120 beats min−1), a Holter ECG recording, and a response to atropine test. During the tests the heart block remained unchanged. Holter monitoring revealed a nearly permanent CAVHB, but with a few 1st or 2nd degree atrioventricular heart block periods. This heart block appeared to be an acquired supra-Hissian block, therefore bundle of His ECG was not recorded. As the patient remained asymptomatic from 1st, 2nd or 3rd AVHB during follow-up and had adequate exercise tolerance, the cardiologist ruled out any indication for implanting a permanent cardiac pacemaker (class II pacing indication11) . The risks and benefits of ESWL were discussed with both the cardiologist and the patient. They agreed to lithotripsy treatment without a temporary transvenous cardiac pacemaker. The patient received no premedication. The patient's preanaesthesia arterial blood pressure was 158/76 mmHg, heart rate was 47 beats min−1. The ECG showed the CAVHB with a Q-T interval of 0.40s. Atropine 1.5 mg was given i.v. to increase the ventricular rate, which reached 79 beats min−1. Following ultrasound localization of the renal stones, treatment of the lower caliceal stone was started. After ≈400 shocks, the patient complained of progressive pain, so was given fentanyl i.v. (50 μg). As the patient's pulse rate decreased to 60 beats min−1, an additional dose of atropine (0.5mg) was given. For about 35 min, 1400 shocks were triggered on the lower caliceal stone. Thereafter the upper calyx calculus was treated with 400 shocks for 10 min. The patient was given a total dose of fentanyl 150 μg over the whole treatment period. During ESWL the patient presented some premature supraventricular or ventricular contractions, but without runs of extrasystoles and the CAVHB remained. No complications occurred post-operatively.
ESWL in a patient with heart block may elicit dysrhythmias or depress the conduction system.
Cardiac dysrhythmias have been observed since the earliest shock wave lithotripsy. Lithotriptors which use a spark gap generator were designed to fire about 20 ms after the R wave of the QRS complex, i.e. during the absolute refractory period. This practice has significantly decreased the risk from extrasystoles. The exact mechanism by which the shock waves cause extrasystoles is unknown. Plasma catecholamine levels were not found to be involved . When firing without ECG triggering, solitary ventricular extrasystoles have occurred, so it has been suggested that these dysrhythmias are related to direct mechanical stimulation of the shock wave on the heart . ESWL treatments, using a spark plug lithotriptor, without coupling of the generator to the electrocardiograph were recently reported. During these nonsynchronized treatments unifocal ventricular premature contractions occurred in 18.4%, and were more frequent during right sided treatments . In the piezoelectric lithotriptors, cardiac dysrhythmias were not thought to be induced and triggering from the ECG was considered unnecessary. But it was recently found that various irregularities of the rhythm can be caused even by treatment using piezoelectric energy . The occurence of dysrhythmias was similar during treatment on the right or left side . Usually dysrhythmias are self limited when the shocks are discontinued, but cases of supraventricular or ventricular tachycardia have been reported .
Furthermore, pain, stress or visceral stimulation may increase vagal [8,10] or sympathetic tone. Moreover, patients receiving opioids were found to have a decreased heart rate. In addition to slowing the rate of sinus mode discharge, fentanyl also prolongs A-V nodal conduction. If bradycardia occurs, Q-T interval is prolonged and torsades de pointes may result. In the present case atropine was given to increase the heart rate and decrease the Q-T interval. The placement of a temporary cardiac pacemaker would have been a simple and hardly a time consuming procedure. On the other hand, the use of i.v. pacemaker carries the risk of complications including infection, thrombosis or intra-operative failure. During the treatment emergency transvenous and transcutaneous pacemaker kits were immediately available and medication for haemodynamic support, such as isoprenaline, were present and ready for use.
In conclusion, ESWL treatment was performed successfully without complications for a patient with CAVHB; however, more experience is needed before ESWL without pacing could be recommended for these patients.
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