Symptomatic Supraventricular Tachycardia Research Articles

Electrophysiology Issues In Adult Congenital Heart Disease

Improved surgical outcomes in children have led to a growing population of adults with congenital heart disease. Rhythm disturbances in the adult congenital heart disease (ACHD) patient can be intrinsic to the anomaly or acquired after palliation. Tachyarrhythmias, either supraventricular or ventricular, and bradyarrhythmias, either sinus node dysfunction or atrioventricular block, may occur frequently. Technological advances in intervention and surgical approaches have led to prophylactic and therapeutic reduction in arrhythmias. In order of escalation, this article addresses medical management, catheter ablation, device therapy for antitachycardia pacing and defibrillation, and surgical intervention. There are now an estimated one million-plus ACHD patients living in the United States. An estimated 45% of those have simple defects (e.g., atrial septal defects), 40% have moderately complex defects (e.g., tetralogy of Fallot, or ToF), and 15% have severely complex defects (e.g., single ventricle anatomy or surgical palliations for transposition of the great arteries [TGA]). The moderate and severe categories have a high incidence of arrhythmia. Of older repaired ToF patients, 34% develop symptomatic atrial or supraventricular tachycardias, 8.5% develop high-grade ventricular tachycardia (VT), and there are an increasing number of implantable defibrillators due to a sudden-death estimate of 2% per decade. Thus, an estimated 50,000 adults with repaired ToF will require electrophysiology follow-up with 100 sudden deaths per year nationally. Roughly 3% of all congenital heart surgeries requiring cardiopulmonary bypass have post-operative AV block, and 1% will require permanent pacing. Older atriopulmonary Fontans have up to an estimated 50% incidence of atrial tachycardia within a decade of palliation due to suture lines and elevated atrial pressures. Patients who have undergone an atrial switch operation (e.g., Mustard or Senning operations) are rarely exclusively in sinus rhythm a decade after repair, thus posing problems for rhythm control and anticoagulation. Catheter ablation in congenital heart disease is often more challenging than structurally normal hearts because of abnormal anatomy (congenital and/or post-surgical) and thicker chamber walls due to unfavorable hemodynamics. In preparation, review of noninvasive imaging, previous catheterization angiography, and surgical palliation reports are paramount prior to a procedure. Fortunately, to meet the growing challenge, newer software with 3-D packages allow for improved mapping. In addition, advances with larger-tipped and irrigated-tip catheters allow for deeper, more effective lesions to be placed. Several advances in surgical approach have led to a reduction in arrhythmias. For example, the arterial switch operation for d-transposition of the great arteries instead of the aforementioned atrial switch operation eliminates the use of a systemic right ventricle that can later develop intra-atrial reentrant tachycardia and sinus node dysfunction. Other advances include paying careful attention to minimizing ventriculotomies in ToF and ventricular septal defect (VSD) repairs, earlier complete repairs, and valve sparing to reduce pulmonary insufficiency. Finally, completion of the extra-cardiac Fontan procedure (e.g., total cavopulmonary connection) for single ventricles avoids extensive suture lines in the right atrium, thereby reducing scarring and higher pressures that lead to IART and sinus node dysfunction. Extracardiac (EC) conduits and lateral tunnel (LT) Fontans are preferred today, and the Fontan conversion procedure (converting prior atriopulmonary Fontans to the EC or LT type) can be performed to reduce arrhythmia and thromboembolic events.

Supraventricular Tachycardia: Diagnosis and Management

Supraventricular tachycardia (SVT) includes all forms of tachycardia that either arise above the bifurcation of the bundle of His or that have mechanisms dependent on the bundle of His. We conducted a review of the techniques used to differentiate the mechanisms of SVT. We searched the PubMed and MEDLINE databases for English-language literature published from 1970 to 2008. Articles were selected for either their historical importance or up-to-date clinical data. This review focuses on techniques for scrutinizing electrocardiograms of patients, analyzing in particular the onset of tachycardia, the mode of tachycardia termination, and the effects of premature ventricular contractions, premature atrial contractions, and aberrancy during tachycardia. Both short-term and long-term management of SVT are examined, including the urgent treatment of patients in the emergency department. This review also describes management of patients who have ongoing symptomatic SVT, outlining such available treatment options as atrioventricular node-blocking drugs, antiarrhythmic drugs, and catheter ablation.

Acute renal insufficiency, supraventricular tachycardia, and confusion after recombinant human bone morphogenetic protein-2 implantation for lumbosacral spine fusion

The authors report on a case of a patient who received recombinant human bone morphogenetic protein-2 (rhBMP-2) to augment spinal fusion for the first and third of 3 lumbosacral fusion surgeries. After receiving rhBMP-2 the first time, the patient became febrile and developed mild acute renal insufficiency and transient supraventricular tachycardia (SVT). The second operation was complicated only by perioperative fever. When the patient received rhBMP-2 again during the third operation, he developed fever, acute oliguric renal insufficiency, symptomatic SVT with hypoxemia, confusion, and joint pain. No clear cause of these problems was identified; however serum analysis revealed the presence of an antibody to rhBMP-2. The authors discuss potential mechanisms for the patient's putative reaction to rhBMP-2, as the findings from a literature review suggest this is the first such reaction to be reported.

Komplikationen nach Ablation supraventrikulärer Tachykardien

The ablation of supraventricular tachycardias is a curative procedure with high success rates. Due to considerably improvement of quality of life, it becomes the therapy of first choice in nearly all kinds of symptomatic supraventricular reentry tachycardias. Following the guidelines for the management of patients with atrial fibrillation, pulmonary vein isolation is still second choice of therapy after ineffective medical treatment. In experienced electrophysiological centres a complication rate of < 2% and an intention to treat mortality of < 0.1% can be expected.

Intermittent fasciculoventricular pathway: ECG and electrophysiologic findings, clinical implications

Although fasciculoventricular (FV) pathways never participate into tachycardia circuits, they give rise to ventricular pre-excitation of variable magnitude which can be source of ECG misinterpretation when associated to other supraventricular rhythm disorders. We report an intermittent FV pathway coincidentally unmasked during an electrophysiologic study performed for a symptomatic supraventricular tachycardia (atrial tachycardia). The clinical context, ECG and EP findings, and therapeutic options are described. Fasciculoventricular pathways need no medical or ablative treatment, thus their positive and differential diagnosis must be clearly assessed.

Clinical Aspects and Prognosis of Brugada Syndrome in Children

Brugada syndrome is an arrhythmogenic disease characterized by an ECG pattern of ST-segment elevation in the right precordial leads and augmented risk of sudden cardiac death. Little is known about the clinical presentation and prognosis of this disease in children. Thirty children affected by Brugada syndrome who were <16 years of age (mean, 8+/-4 years) were included. All patients displayed a type I ECG pattern before or after drug provocation challenge. Diagnosis of Brugada syndrome was made under the following circumstances: aborted sudden death (n=1), syncope of unexplained origin (n=10), symptomatic supraventricular tachycardia (n=1), suspicious ECG (n=1), and family screening for Brugada syndrome (n=17). Syncope was precipitated by fever in 5 cases. Ten of 11 symptomatic patients displayed a spontaneous type I ECG. An implantable cardioverter-defibrillator was implanted in 5 children; 4 children were treated with hydroquinidine; and 1 child received a pacemaker because of symptomatic sick sinus syndrome. During a mean follow-up of 37+/-23 months, 1 child experienced sudden cardiac death, and 2 children received an appropriate implantable cardioverter-defibrillator shock; all of them were symptomatic and had manifested a type I ECG spontaneously. One child had a cardioverter-defibrillator infection that required explantation of the defibrillator. In the largest population of children affected by Brugada syndrome described to date, fever represented the most important precipitating factor for arrhythmic events, and as in the adult population, the risk of arrhythmic events was higher in previously symptomatic patients and in those displaying a spontaneous type I ECG.

C-type natriuretic peptide in individuals with normal left ventricular systolic function

Objective. The objective of this study was to evaluate production or release of CNP in individuals without CHF. Methods. Nineteen patients with symptomatic paroxysmal supraventricular tachycardia (PSVT) and normal left ventricular systolic function were enrolled into the study. Blood samples were collected from the coronary sinus (CS), the femoral artery (FA), and the peripheral vein (PV) before pacing, after rapid RA pacing, and post electrophysiological study (EPS) and/or radiofrequency (RF) ablation. Results. The CNP level in the CS, compared to FA and PV, was significantly higher before pacing (CS, 3.2±0.8; FA, 2.6±0.7; PV, 2.5±0.5 pg/ml; CS vs. either FA or PV, both p<0.001), after the pacing (CS, 3.2±1.3; FA, 2.4±0.6 pg/ml; p=0.004), and post the EPS and/or RF ablation (CS, 3.1±0.7; FA, 2.6±0.9; PV, 2.5±0.8 pg/ml; CS vs. either FA or PV, both p<0.01). Conclusion. The myocardium regularly produces or releases CNP in patients with normal LV systolic function. Brief periods of rapid RA pacing, PSVT, or EPS does not change the production and/or release.

When to Perform Catheter Ablation in Asymptomatic Patients With a Wolff-Parkinson-White Electrocardiogram

What to do when a person without any cardiac complaint shows a Wolff-Parkinson-White (WPW) pattern on the ECG has been an important question for more than 2 decades. Recent articles by Pappone et al1–3 make it necessary to revisit that question. Epidemiological data indicate that 0.1% to 0.3% of the general population have ECG findings suggesting that during sinus rhythm, in addition to AV conduction over the AV node His pathway, there is also AV conduction over an accessory AV pathway (AP).4 This means that each year ≈4 new cases are found in a population of 100 000. It is also known that there is a 4-fold increase of this finding in family members of WPW patients.5 The WPW patient is often symptomatic because of cardiac arrhythmias. When arrhythmias are present, the disorder is called the WPW syndrome. The 2 most common types of arrhythmia in the WPW syndrome are (1) a circus movement tachycardia (CMT), also called an AV reentrant tachycardia, in which AV conduction goes by way of the normal AV conduction system and VA conduction over the AP and (2) atrial fibrillation (AF).6 AF can be a life-threatening arrhythmia in the WPW syndrome if the AV AP has a short anterograde refractory period (RP), allowing many atrial impulses to be conducted to the ventricle. That will result in very high ventricular rates with possible deterioration into ventricular fibrillation (VF) and sudden death.7,8 A CMT that in general is well tolerated by the patient when additional heart disease is absent may deteriorate into AF, and the ventricular rate and risk for VF will depend on the anterograde RP of the AP. Therefore, the most important question in the asymptomatic WPW patient in whom the typical ECG accidentally is recorded is whether he or …

Successful Radiofrequency Catheter Ablation of Left Lateral Accessory Pathway Using Transseptal Approach During Pregnancy

Recurrent supraventricular tachycardia (SVT) associated with the Wolff-Parkinson-White syndrome during pregnancy may be difficult to manage, mainly due to concerns about the effects of pharmacotherapy on the fetus. We report on a 32 year old woman in her 22nd week of pregnancy with recurrent symptomatic SVT in which standard pharmacotherapy had been ineffectual, contraindicated or poorly tolerated and in whom we were able to perform a successful transseptal ablation of a left lateral accessory pathway.

Incessant tachycardia following catheter ablation of an accessory pathway: What is the mechanism?

A 16-year-old male with a history of symptomatic supraventricular tachycardia refractory to medical therapy and evidence of preexcitation on surface ECG was referred for catheter ablation. Baseline 12-lead ECG and the induced tachycardia are shown in Figure 1. AH interval was 45 ms, HV interval was 0 ms, and QRS duration was 134 ms. Retrograde activation of the atria during orthodromic tachycardia was believed to be utilizing two right-sided accessory pathways (APs). His-refractory premature ventricular complexes delivered in the right ventricle during tachycardia advanced the subsequent atrial activation, showing participation of at least one of the pathways in the retrograde limb of the tachycardia. Ventricular burst pacing always terminated the tachycardia. Catheter ablation of the manifest AP was performed, and the postablation intervals were AH: 118 ms, HV: 45 ms, and QRS duration: 84 ms. Following ablation, the tachycardia utilizing the second (concealed) AP became incessant (Figure 2). What is the mechanism of the incessant tachycardia? Why did the tachycardia become incessant after the ablation of the first pathway? Figure 2Intracardiac recording after ablation of the manifest accessory pathway showing a sinus beat reinitiating tachycardia (arrow). HRA = right atrial catheter; His p = His-bundle proximal; His m = His-bundle mid; His d = His-bundle distal; CS OS = coronary sinus ostium; CS DIST = coronary sinus distal; RVa = right ventricular apex. View Large Image Figure Viewer

N-terminal pro-atrial natriuretic peptide as a biochemical marker of long-term interventional success after radiofrequency catheter ablation of paroxysmal supraventricular tachyarrhythmias

Radiofrequency (RF) catheter ablation has been shown to be highly effective in the treatment of supraventricular tachycardias. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (B-type natriuretic peptide; BNP) are secreted by the heart mainly in response to myocardial stretch induced by volume load. The aim of the present study was to determine the time course of the N-terminal prohormone forms of ANP (NT-proANP) and BNP (NT-proBNP) in patients undergoing radiofrequency (RF) catheter ablation for paroxysmal supraventricular tachycardias. Serial blood samples were taken from 13 patients with symptomatic paroxysmal supraventricular tachycardias undergoing RF ablation and from 13 age- and gender-matched healthy controls. Blood was taken before ablation (day 0, baseline), and at day one and day 120 after ablation. Levels of NT-proANP were significantly higher before RF ablation (4862+/-726 pmol/l) as compared to day one (2021+/-220 pmol/l) and day 120 after RF ablation (2470+/-349 pmol/l) (with p<0.01 on day one and p<0.05 on day 120; n=13). The size of the left atrium decreased from 41.0+/-5.5 mm before ablation to 34.9+/-5.9 mm (n=13; p<0.05) on day 120 as measured by M-mode echocardiography. Levels of NT-proBNP showed comparable values before and on day one and day 120 after ablation and were not significantly elevated as compared to healthy controls. NT-proANP levels are increased in patients presenting with paroxysmal supraventricular tachycardias and decrease one day after radiofrequency catheter ablation, possibly reflecting a transient reduction of ANP secretion from injured myocardial cells. Lower NT-proANP levels in the long-term time course may result from reduction of atrial volume load and reconstitution of atrial architecture after successful treatment of supraventricular tachycardias. NT-proANP may serve as a useful laboratory marker to describe the long-term interventional success after RF ablation.

Usefulness of invasive electrophysiologic testing to stratify the risk of arrhythmic events in asymptomatic patients with Wolff-Parkinson-White pattern: Results from a large prospective long-term follow-up study

ObjectivesThe aim of this study was to assess in a large cohort of asymptomatic subjects with Wolff-Parkinson-White (WPW) pattern the usefulness of invasive electrophysiologic testing (EPT) in predicting the occurrence of arrhythmic events over a five-year follow-up. BackgroundSudden death may be the first clinical manifestation of the WPW syndrome in previously asymptomatic patients. Serial EPTs have been proposed to identify patients at risk. MethodsA total of 212 consecutive asymptomatic WPW patients were enrolled after a baseline EPT; patients were followed for five years, and 162 patients (115 noninducible and 47 inducible) patients underwent a second EPT. ResultsAfter a mean follow-up of 37.7 months, 33 patients became symptomatic. Of the 115 noninducible patients, 18.2% lost anterograde accessory pathway (AP) conduction, 30% retrograde AP conduction, and only 4 (3.4%) developed symptomatic supraventricular tachycardia (SVT). Of the 47 inducible patients, 25 with sustained atrioventricular reciprocating tachycardia (AVRT) and atrial fibrillation (AF), and 4 with nonsustained AVRT and AF became symptomatic for SVT (n = 21) and AF (n = 8). They were younger, had shorter AP anterograde refractory periods, and multiple APs compared to patients who remained asymptomatic (for all comparisons, p < 0.0001). Of the eight patients with symptomatic episodes of AF and inducible sustained AF, two had a resuscitated cardiac arrest and one died suddenly; all three patients were inducible for AVRT and AF and had multiple APs. ConclusionsIn asymptomatic WPW subjects, EPT may be a valuable tool to stratify the risk of symptomatic and fatal arrhythmic events.

Abbreviated combined anatomical/electrophysiological approach for catheter ablation of atrioventricular nodal reentrant tachycardia in children.

Atrioventricular nodal reentrant tachycardia was proven during electrophysiologic study in 41 children, aged from 3.7 to 16 years, who were referred for catheter ablation of symptomatic supraventricular tachycardia. Using an abbreviated combined anatomical and electrogram-guided approach for selective ablation of the slow pathway, a steerable ablation catheter was placed at the inferior region of the vestibule of the tricuspid valve close to the orifice of the coronary sinus, with the intention of recording a multicomponent local atrial electrogramm during sinus rhythm. If application of radiofrequency current of 500 kHz at 70 degrees C at this site did not result in a slowly accelerated junctional rhythm, at a rate of less than 120 beats per minute, the catheter was stepwise advanced up to a position midway towards the apex of the triangle of Koch for additional applications of energy. Ablation was achieved in 35 of the patients. In 6 patients, the slow pathway was modulated such that the tachycardia could no longer be induced. The number of applications of energy ranged from 1 to 19, with a median of 6 applications. The mean period of fluoroscopy was reduced to 15.6 (4.3 to 39.8) minutes, while the overall duration of the catheterization procedures ranged from 88 to 280 (mean 173.2) minutes. In none of the patients did we observe permanent high grade atrioventricular block. During follow-up over a mean of 4.1 years, two patients had recurrence of tachycardia, corresponding to a 95% rate of success in the midterm. We conclude that selective radiofrequency ablation of the slow pathway using the abbreviated anatomical and electrophysiological approach is a safe and curative therapeutic approach in children with atrioventricular nodal reentrant tachycardia. Periods required for fluoroscopy can be significantly reduced, and mid-term results are excellent.

Ablación mediante radiofrecuencia de una vía accesoria en un lactante con esclerosis tuberosa y rabdomiomas cardíacos

Rhabdomyomas may be the underlying cause of accessory pathways in patients with tuberous sclerosis, leading to symptomatic supraventricular tachycardia that does not respond to antiarrhythmic drugs. We report an infant with tuberous sclerosis and cardiac rhabdomyomas who underwent successful radiofrequency catheter ablation of a left free wall accessory pathway and we describe the clinical features, ablation findings and long-term follow-up.

Daily Variations in the Occurrence of Symptomatic Supraventricular Tachycardia as Determined by Ambulatory Event Monitoring

The diurnal incidence of supraventricular tachycardia (SVT), including atrial fibrillation and atrial flutter, has been quantified by examining 7,891 cases of symptomatic arrhythmia in 5,869 patients assigned to ambulatory monitoring using electrocardiographic event recorders with transtelephonic reporting. The probability of occurrence of SVT was found to be high and moderately variable throughout the normally active hours of the day between 8 a.m. and 8 p.m. and to be uniformly low during the inactive hours between 1 and 5 a.m. Age-related peaks within the active phase were independently associated with the older half of the study population (9 a. m.) and with the younger half (6 p. m.). The daily incidence of SVT is primarily characterized by 2 states of activity, active and quiescent. Quiescence of SVT is associated with normal sleep and inactivity.

Results of Radiofrequency Ablation in Patients With Clinically Documented, but Noninducible, Atrioventricular Node Reentrant Tachycardia and Orthodromic Atrioventricular Reciprocating Tachycardia

Among 1,281 patients with symptomatic supraventricular tachycardia, 34 patients (2.7%) with presumed diagnosis of atrioventricular node reentrant tachycardia and orthodromic atrioventricular reciprocating tachycardia did not have inducible tachycardia in the electrophysiologic laboratory. Application of radiofrequency energy to the presumed arrhythmogenic sites could achieve a high success rate, with a low recurrence rate in these patients.

Alterations in heart rate following radiofrequency ablation in the treatment of reentrant supraventricular arrhythmias: relation to alterations in autonomic tone.

To determine the relation between the creation of endocardial lesions and alterations in autonomic tone, we analyzed heart rate variability in patients undergoing radiofrequency catheter ablation for symptomatic supraventricular tachycardia. Elevated heart rates are frequently noted after radiofrequency catheter ablation for supraventricular arrhythmias. It has been postulated that this elevation may be secondary to alterations in cardiac autonomic tone. Since heart rate variability is a measure of autonomic nervous system activity, we used this technique to examine the heart rate elevation and to characterize postablation autonomic changes. Thirty-eight patients undergoing 44 radiofrequency catheter ablation procedures were included in the study. Total arrhythmic substrates treated included 34 accessory pathways and 13 AV nodes with dual physiology. Twenty-four hour ambulatory electrocardiographic recordings were obtained in a drug-free state prior to, ablation early postablation, and late postablation. Spectral and nonspectral analyses of heart rate variability were performed. Subgroup analyses were also done on specific cohorts. Subgroups included patients undergoing accessory pathway ablations, AV node modifications, and ablation of septal and nonseptal targets. To determine whether the amount of tissue damage was related to changes in heart rate variability, we analyzed the relation between the total energy delivered to the endocardium and the peak change in creatine kinase and heart rate variability. In this population, a significant transient increase in heart rate was noted following radiofrequency ablation. All time and frequency domain parameters of heart rate variability showed significant reversible decreases. These changes were independent of target site and arrhythmia substrate. There was no correlation noted between the changes in heart rate variability and either the total amount of energy applied to the endocardium or the change in creatine kinase. Increased heart rates and decreased heart rate variability occur following radiofrequency catheter ablation for supraventricular tachycardia. Clinically, the predominant effect is that of decreased parasympathetic tone. Since these transient changes are independent of arrhythmic substrate or ablation site in the atria, a rich parasympathetic innervation of the heart is proposed.

Radiofrequency catheter ablation of left-sided accessory pathways using a transeptal technique and specialized long intravascular sheaths. Efficacy, recurrence rate and complications.

49 patients with 51 left-sided accessory pathways underwent radiofrequency catheter ablation for symptomatic supraventricular tachycardia via the transeptal route using specialised long vascular sheaths with compound curves. The procedure was successful in 45 patients (92%). The mean fluroscopic time was 22.5 +/- 15.2 mins and the mean procedure time was 1.7 +/- 0.5 hours. Pericardial tamponade occurred in 2 patients (4%) and 2 patients (4%) required switching to the retrograde transaortic route for successful ablation of the pathways. During the period of follow-up of 16.8 +/- 6.9 months, clinical recurrence occurred in 2 patients (4%). In conclusion, the transeptal route of radiofrequency catheter ablation is a useful alternative strategy to the transaortic approach with good long term results. The use of specialised sheaths may help in stabilisation of the catheter during the procedure which can generate more adequate lesions and consequently a lower recurrence rate.

Efficacy and safely of long-term oral flecamide acetate in patients with responsive supraventricular tachycardia

In 102 patients with inducible supraventricular tachycardia (SVT), 56 women and 46 men aged 20–86 (mean, 52) years, underwent electrophysiologic study. SVTs observed at electrophysiologic study were atrial flutter or atrial fibrillation (32%), the “slow-fast” form of atrioventricular (AV) nodal reentrant tachycardia (45%), orthodromic AV reentrant tachycardia (25%), and atrial tachycardia (9%). More than 1 SVT occurred in some patients. Spontaneous symptomatic SVT frequency prior to oral flecainide varied from 3/day to 1/3 months (mean, 3/month). At electrophysiologic study and during SVT, intravenous flecainide, 2 mg/kg body weight, was given at an infusion rate of 10 mg/min up to a maximum dose of 150 mg. Patients were commenced on oral flecainide if SVT termination occurred during intravenous flecainide administration and if reinitiation was not possible after the total dose of flecainide had been given. In patients with AV nodal reentrant tachycardia and AV reentrant tachycardia further criteria for commencing oral flecainide were SVT termination by ventricularatrial conduction block and persistent ventricularatrial block after intravenous flecainide administration. Initial oral flecainide dosage was determined by assessing ability to reinitiate SVT after 50 mg, 100 mg, and the total dose of intravenous flecainide had been given. Eighty-nine patients (87%) remained free of symptomatic SVT over a mean follow-up period of 3.9 years (range, 3 months to 6.5 years). Two thirds were still taking the original dosage of flecainide and the rest were SVT-free on a higher dosage. Oral dosages ranged from 50 to 300 mg/day (median dosage, 100 mg twice daily) Nine patients experienced minor side effects, including lethargy, dizziness, headache, and blurred vision. There were no deaths and no reports of major proarrhythmic events or other major adverse effects.

Effects of pregnancy on first onset and symptoms of paroxysmal supraventricular tachycardia

It is important for women to understand the risk of first onset and symptomatic exacerbation of paroxysmal supraventricular tachycardia (SVT) during pregnancy. Reports regarding the effects of pregnancy on first onset and symptomatic exacerbation of paroxysmal SVT have been controversial, and have not been conducted in a systematic fashion. Two hundred seven consecutive female patients diagnosed with symptomatic paroxysmal SVT were requested to respond to multiple questionnaires before electrophysiologic study and catheter ablation. A person-years data method was used to estimate risk of first onset of paroxysmal SVT during pregnancy. Exacerbation of paroxysmal SVT was assessed by a score scale including each of the following symptoms: palpitation, fatigue, rest dyspnea, effort dyspnea, dizziness, chest oppression, blurred vision, and syncope (total score change > 2 points). In the 107 patients with accessory pathway-mediated tachycardia, 7 patients had had a first onset of tachycardia during pregnancy (relative risk ratio 0.86, confidence interval 0.4 to 1.9, p = 0.35). In the 100 patients with atrioventricular nodal reentrant tachycardia, 1 patient had had the first onset of tachycardia during pregnancy (relative risk ratio 0.11, confidence interval 0.02 to 0.56, p = 0.004). Otherwise, 14 of the 63 patients (22%) with tachycardia in the pregnant and nonpregnant periods had exacerbation of symptoms during pregnancy. Thus, first onset of paroxysmal SVT during pregnancy was rare (3.9%), and pregnancy was associated with a low risk of first onset of paroxysmal SVT. However, symptoms of paroxysmal SVT were exacerbated during pregnancy in some patients.