SYMPTOMS

Eighty patients (51%; 55 male and 25 female) were symptomatic at diagnosis (77) or developed symptoms (brief palpitations) during the follow up period (3). Symptoms were palpitations in 65, history of syncope in 10, and both in five. Seventy seven patients (49%) were totally asymptomatic (53 male and 24 female). Mean (SD) age at study entry was 38.5 (20.6) years for symptomatic subjectsv 46.7 (21.0) for the asymptomatic subjects (p < 0.03).

ARRHYTHMIAS

Thirty nine arrhythmias were documented in 38 patients (24.2%), 31 male (mean age 34.1 (19.2) years) and seven female (mean age 52.3 (22.0) years). The difference between the two sexes was not significant either in incidence or in age. Supraventricular tachycardias (orthodromic and antidromic) were recorded in 27 patients (mean age 31.5 (19.4) years), including two infants, 23 men (mean age 31.2 (17.4) years), and four women (mean age 36.3 (13.0) years). Antidromic supraventricular tachycardias were documented in two patients. Atrial fibrillation was recorded in 12 patients (mean age 52.1 (20.5) years), nine men (mean age 46.9 (19.8) years) and three women (mean age 68.0 (13.9) years) (fig 2). In 11 of 12 cases, atrial fibrillation was the first arrhythmic event and in one man with a history of supraventricular tachycardias, atrial fibrillation appeared later. Onset of atrial fibrillation appeared in older patients than supraventricular tachycardia (p < 0.01, table 2). Three patients with atrial fibrillation (1) or supraventricular tachycardia (2) also had a history of syncope or near syncope.

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Figure 2

Age at onset of first arrhythmic event in patients with Wolff-Parkinson-White syndrome in north west Greece. AF, atrial fibrillation; CMT, circus movement tachycardia.

ACCESSORY PATHWAY LOCATION

There was an excess of left sided (54%)v right sided (46%) pathways: left anterolateral, 35 (22%); left posterolateral, 27 (17%); left posteroseptal, 20 (13%); right anterolateral, 20 (13%); right midseptal, 21 (13%); right posteroseptal, 13 (8%); right anteroseptal, 12 (8%). Forty two per cent of the bypass tracts were septally located. We were not able to identify the accessory pathway location in nine ECGs (6%). There was no difference in age or sex among the eight groups of pathway location.

The accessory pathway location in patients with supraventricular tachycardias was: left lateral, 14; septal, 12; right lateral, 3; in patients with atrial fibrillation it was: septal, 6; left lateral, 5; right lateral, 1. Ten (67%) of the patients with syncope or near syncope had a septally located accessory pathway.

COEXISTENCE OF CARDIAC DISEASE

Thirteen patients had a history of cardiac disease: nine had coronary artery disease, two had mitral regurgitation, one had mitral valve prolapse, and one had cardiomyopathy associated with supraventricular tachycardia. None of the patients had congenital heart disease.

PREGNANCY

We identified four pregnant women (three asymptomatic, one with palpitations) with WPW pattern. A fifth woman, with known symptomatic WPW syndrome, experienced more palpitations during pregnancy.

WPW PATTERN IN CANDIDATES FOR OPERATIONS

Preoperatively we identified 19 new cases of WPW pattern (14 men, five women). The mean age was 41.4 (22.4) years for men and 56.2 (15.1) years for women. There was no significant difference in age at diagnosis or sex between these patients and the remainder (age at diagnosis, 39.3 (21.1) years for male patients (n = 94) and 49.7 (21.3) years for female patients (n = 44)). Although the incidence of newly detected WPW in this group appeared somewhat increased (5.4/100 000 candidates/year), it was not significantly different from the overall incidence in north west Greece.

MEDICAL TREATMENT

Sixteen patients (11 men and five women) were receiving medical treatment. Drugs used were amiodarone (7), sotalol (1), propafenone (3), disopyramide (1), verapamil (2), and β blockers (2). Compliance with the drug regimen was relatively poor in this group.

CLINICAL COURSE

Based on a mean follow up period of 55 months (range 20 to 108 months), the cumulative observation period was 720 patient-years. During the study period three of the 80 asymptomatic patients (3.7%) had palpitations. Ten patients (nine men, one woman), mean age 38.5 (17.1) years, nine of whom were symptomatic, underwent transcatheter ablation of the accessory connection using radiofrequency energy. The indication for the procedure was recurrent episodes of tachycardia in eight patients (three with atrial fibrillation, five with supraventricular tachycardias) and syncope in one patient. Ablation was also performed in one asymptomatic athlete involved in competitive sports. There were three recurrences of ventricular pre-excitation after the intervention.

Six patients died during follow up, none suddenly. Fatal myocardial infarction was responsible in two cases, malignancy in three, and intracranial haemorrhage in one. One of these six patients, who died during a colon cancer operation, had a history of palpitations.

DEMOGRAPHIC FEATURES

This study involved a follow up of a group of patients with pre-excitation referred to the national health system services of north west Greece for various, not purely cardiac, reasons. The incidence for new cases was 4.4/100 000/year and the incidence in males was more than twice that in females. However, it is nor possible to determine the precise incidence of WPW pattern because of its intermittent nature. The incidence found in our study was approximately the same as the overall incidence of new cases of WPW in the Olmsted County study.5 The increased frequency in males is in accordance with previous reports3 ,5 ,10; however, Sanoet al recently reported a 1:1 male to female ratio in Japanese schoolchildren with ventricular pre-excitation.11 The highest incidence in female subjects in our study was during the seventh decade (fig 1). Interestingly this peak has not been reported in other studies. Men were significantly younger than women at first diagnosis. The reasons for these sex differences are not known but it has been suggested that women are cared for and treated differently for a variety of diseases. In Greece, women live longer than men and there are no differences between them in health insurance. Despite the fact that unpublished data from our area have shown no sex bias for coronary intervention (Goudevenos J, Giogiakas V, Michalis LK, et al. XIX Congress of the European Society of Cardiology, Stockholm, August 24–28, 1997; Goudevenos J, Pappas K, Giogiakas V, et al. XXth Congress of the European Society of Cardiology, Vienna, August 22–26, 1998), we cannot exclude the possibility that women's access to health care is less or later in their life than men's. However, the fact that the overall incidence, male to female ratio, and mean age at diagnosis were not different from those in the preoperative cases (who were clearly not screened for the WPW syndrome) may indicate that our findings in the general population were fairly representative.

SUDDEN DEATH

Sudden death is fortunately a rare event but may be the first manifestation of the syndrome in previously asymptomatic individuals.12 The estimated incidence in both patients with pre-excitation pattern and those with complete WPW syndrome ranges from 0 to 0.006 per patient-year.3 ,5-7 ,13 In the present study no sudden death occurred in 720 patient-years. None of the six deaths reported was attributable to a primary arrhythmia. There may be various reasons for the absence of this fatal complication. First, 720 patient-years is not enough. Second, the majority of patients were asymptomatic or nearly asymptomatic; previous studies have shown that patients who were asymptomatic at diagnosis do extremely well and are not liable to sudden cardiac death.5 ,10 Third, most of the study participants had no organic disease. Finally, some individuals with a bypass tract would not have been identified, so patients with WPW syndrome may have died suddenly without an ECG diagnosis having been made. Topazet al showed that among 23 young patients resuscitated from sudden cardiac death, three (14%) had WPW syndrome, but it is worth noting that two of these three patients had a past history of palpitations.14

ATRIAL FIBRILLATION

Atrial fibrillation is not a rare arrhythmia in WPW syndrome. It is clinically important because extremely rapid rates can occur over the bypass tract, leading to haemodynamic deterioration or ventricular fibrillation. In the present study, 12 patients (8.0%) had atrial fibrillation. The incidence of atrial fibrillation was somewhat lower than other values reported (11% to 30%),15-19 mainly because of the relatively large number of asymptomatic patients in our study. The mean age of the atrial fibrillation group was greater than that of patients with circus movement tachycardias.

SUPRAVENTRICULAR TACHYCARDIAS

The most common tachycardias associated with WPW syndrome are circus movement tachycardias.20 In our study 93% of these were orthodromic and this is in accordance with previous studies.

SYMPTOMS

Almost half of our study cohort reported symptoms. The symptomatic patients were significantly younger than the asymptomatic subjects. Syncope occurred in 15 individuals (9.5%). According to previous studies,21-23 syncope occurs in 11% to 29% of patients with WPW syndrome. Ten (67%) of the patients with syncope or near syncope had a septally located accessory pathway. Timmermanset al reported that the dense innervation of this area could cause extreme shortening of the refractory period of the accessory pathway leading to very fast ventricular response during atrial fibrillation.12 We found no difference in sex or age between patients with and without syncope, and these findings are in agreement with other series.24

COEXISTENCE OF CARDIAC DISEASE

The most common associated cardiac disease was coronary artery disease (6%). We did not find any patient with WPW pattern and congenital heart disease. Although an association between congenital heart lesions with WPW pattern has been reported,5 ,25 our findings are supported by Sano et al,11 suggesting that the combination in a community based population is uncommon.

PREGNANCY

Pregnancy seems to increase the likelihood of arrhythmias and symptoms in women with WPW syndrome.26 ,27 This is because of changes in haemodynamics, hormonal function, and sympathetic tone (increased stress and anxiety). In our study, pregnancy induced symptoms in one previously asymptomatic woman and increased the frequency of palpitations in another.

SYMPTOM STATUS AT DIAGNOSIS AND CLINICAL COURSE

There was approximately a 1:1 ratio between asymptomatic and symptomatic patients, and the most common presenting symptom in the latter group was palpitations. In previous retrospective studies, symptoms have been noted in 60–64% of patients with pre-excitation identified through hospital records.7 ,28 In our study, three individuals asymptomatic at diagnosis developed symptoms (brief palpitations) during the follow up period. This finding suggests that patients asymptomatic at diagnosis tend to remain free of symptoms or tachycardias and have a generally benign prognosis. There is growing interest in the prognosis of asymptomatic subjects with WPW pattern, principally because potentially curative radio frequency ablation might be a management possibility. Several studies have attempted to assess the risk of symptom development in individuals who are asymptomatic at the time of diagnosis of ventricular pre-excitation. Mungeret al reported that 30% of initially asymptomatic individuals developed symptoms related to arrhythmias over a 12 year follow up period.5 In concordance with our findings, other investigators have reported even lower rates of symptom development (0–8%). However, follow up periods have been variable.29 ,30 More importantly, investigators have attempted to assess the risk of sudden cardiac death in asymptomatic patients. In particular, some studies have reported that this fatal event is extremely rare among asymptomatic individuals with WPW pattern, but may occur.3 ,6 ,14 ,31 Recently, Timmermanset al reported that 15 of 690 patients (2.2%) with WPW syndrome who were referred to their hospital over a 16 year period had an aborted sudden cardiac death, and ventricular fibrillation was the first clinical manifestation in eight patients.12 However, that study was a retrospective one, the patients representing a selected population referred to hospital for evaluation and treatment of an arrhythmia, and information about the incidence of sudden cardiac death in asymptomatic individuals with known WPW pattern could not possibly have been obtained. It is not clear also whether the WPW patients who were resuscitated from ventricular fibrillation did or did not have symptoms for which they had consulted a physician before the event (in other words, were patients with no documented arrhythmic events really asymptomatic?). In contrast to these studies, Leitch et alreported no cases of sudden cardiac death in a group of 75 initially asymptomatic patients followed for a mean of 4.3 years.10Similar conclusions about the short term outcome of asymptomatic WPW individuals have been reached by others.29 Moreover, Krahnet al showed that 19 originally healthy men who were not screened for the WPW syndrome or for asymptomatic pre-excitation and were found to have pre-excitation on a routine ECG had an excellent long term prognosis.30 Mungeret al also reported two sudden cardiac deaths among patients with WPW pattern over 1338 patient-years of follow up, but neither of these occurred in patients who were asymptomatic at diagnosis.5 From our results and those of previous reports, it seems that definitive treatment may be postponed until symptoms develop, as only three of 77 asymptomatic cases developed symptoms and no asymptomatic case had syncope or sudden death.

STUDY LIMITATIONS

We attempted to identify as many cases of ventricular pre-excitation as possible in the population of a defined geographical region by collecting data from a variety of health care sources within the region. However, underreporting—either because asymptomatic subjects did not have an ECG or because certain health care providers may have failed to report every case—cannot be excluded, although in the subpopulation of preoperative cases the incidence of new cases was not significantly different from that in the general population.

There was no information about the electrophysiological characteristics of the bypass tract in the majority of the symptomatic and asymptomatic patients.

Localisation of the accessory pathway on the basis of a surface 12 lead ECG rather than by electrophysiological study cannot achieve the highest accuracy. Also, multiple pathways could not be identified. Nonetheless, this study offers a rare opportunity to examine the natural history of a relatively common condition in an unselected population in whom few interventions (pharmacological or non-pharmacological) had taken place.

CONCLUSIONS

In north west Greece the WPW pattern is more common and diagnosed at a younger age in male than in female subjects. Half the patients with a WPW pattern on ECG were asymptomatic (no sex difference) at diagnosis and tended to remain so thereafter. Supraventricular tachycardia appeared at a younger age than atrial fibrillation. No sudden cardiac death occurred during a 720 patient-years follow up period. The prognosis is generally benign.