Circulating electrolytes and the prevalence of atrial fibrillation and supraventricular ectopy: The Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND AND AIMS

Evaluating associations of circulating electrolytes with atrial fibrillation (AF) and burden of supraventricular arrhythmias can give insights into arrhythmia pathogenesis.

METHODS AND RESULTS

We conducted a cross-sectional analysis of 6398 participants of the Atherosclerosis Risk in Communities (ARIC) study, ages 71-90, with data on serum electrolytes (magnesium, calcium, potassium, phosphorus, chloride, sodium). Prevalence of AF was determined from electrocardiograms and history of AF hospitalizations. A subset of 317 participants also underwent electrocardiographic recordings for up to 14 days using the Zio® patch. Burden of other supraventricular arrhythmias [premature atrial contractions (PACs), supraventricular tachycardia] was determined with the Zio® patch. We used logistic and linear regression adjusting for potential confounders to determine associations of electrolytes with arrhythmia prevalence and burden. Among 6394 eligible participants, 614 (10%) had AF. Participants in the top quintiles of magnesium [odds ratio (OR) 0.82, 95% confidence interval (CI) 0.62, 1.08], potassium (OR 0.82, 95%CI 0.68, 1.00), and phosphorus (OR 0.73, 95%CI 0.59, 0.89) had lower AF prevalence compared to those in the bottom quintiles. No clear association was found for circulating chloride, calcium or sodium. Higher concentrations of circulating calcium were associated with lower prevalence of PACs in the 12-lead electrocardiogram, while higher concentrations of potassium, chloride and sodium were associated with higher PAC prevalence. Circulating electrolytes were not significantly associated with burden of PACs or supraventricular tachycardia among 317 participants with extended electrocardiographic monitoring.

CONCLUSION

Concentrations of circulating electrolytes present complex associations with selected supraventricular arrhythmias. Future studies should evaluate underlying mechanisms.

Predictors of High-Sensitivity Cardiac Troponin T Elevation in Patients with Acute Paroxysmal Supraventricular Tachycardia and Ischemic Heart Disease

We studied the predictors and patterns of high-sensitivity cardiac troponin T (hs-cTnT) elevation in patients with paroxysmal supraventricular tachycardia (PSVT) in the presence and absence of ischemic heart disease. During calendar year 2013, we enrolled 70 of 72 consecutive adult patients with PSVT who presented at our center within 4 hours after the onset of tachycardia. On the basis of increased hs-cTnT at either of 2 initial measurements, we divided patients into groups (hs-cTnT-positive and hs-cTnT-negative), to study the predictors of enzyme elevation. We then divided the hs-cTnT-positive patients into 2 groups-those with and those without ischemic heart disease-and compared hs-cTnT changes. We observed hs-cTnT elevation in 52 of the 70 patients (74.3%). The hs-cTnT-positive patients were significantly older (P=0.008) and had a significantly higher duration of tachycardia (P=0.01). Older age, the presence of chest pain, lower diastolic blood pressure, and longer duration of tachycardia increased the odds of enzyme elevation. Among patients with elevated hs-cTnT levels, the baseline and maximal hs-cTnT levels were significantly higher in ischemic patients (P=0.01 and P=0.003, respectively). The increase in hs-cTnT seemed to be higher and longer in ischemic patients, although this was not statistically significant (P=0.908). Finally, hs-cTnT did not decrease to baseline levels within 48 hours in either group. We found that hs-cTnT levels increased in all our patients with PSVT, more so in those with ischemic heart disease.

Characterization of Cardiac Troponin Elevation in the Setting of Pediatric Supraventricular Tachycardia

Cardiac troponin (cTn) is currently considered the gold standard biomarker for detection of myocardial necrosis. Patients with supraventricular tachycardia (SVT) often present with symptoms resulting in cTn assessment; however, there are no data on the results of such testing in childhood. We hypothesized that cTn elevation would be common in the pediatric SVT population and would portend a benign prognosis. A retrospective review of all pediatric patients (≤21 years) presenting with SVT was performed. Clinical and electrocardiographic variables from the emergency department (ED) presentation were reviewed and clinical outcomes during subsequent follow-up assessed. Of 128 patients seen in the ED for SVT, cTn was assessed in 48 (38 %). Of patients with cTn assessment, 14 (29 %) patients demonstrated cTn elevation. Univariate predictors of cTn elevation included presentation with respiratory or gastrointestinal symptoms (50 vs 12 % and 42 vs 9 %; p = 0.008 and p = 0.01, respectively), lower mean arterial blood pressure (73 vs 85 mm Hg, p = 0.009), higher age-adjusted tachycardia rate (z score 9.3 vs 7.2, p < 0.001), and longer tachycardia duration (4.2 vs 1.0 h, p = 0.02). Multivariate logistic regression confirmed the association of age-adjusted tachycardia rate (odds ratio [OR] 3.8 per heart rate z score, confidence interval [CI] 1.9-11.8, p = 0.003) and duration (OR 1.5 per hour, CI 1.1-2.5, p = 0.03). Clinical outcome was excellent with no adverse sequelae during a median of 2.9 years of follow-up. Cardiac Tn elevation is common in the pediatric population presenting with SVT. Episode severity, characterized by respiratory or gastrointestinal symptoms, lower mean blood pressure, and increased tachycardia rate and duration are predictive. Clinical follow-up is favorable.

Assessment of the neutrophil/lymphocyte ratio in patients with supraventricular tachycardia

OBJECTIVE

The neutrophil/lymphocyte ratio (NLR) has been evaluated as a new predictor of cardiovascular risk. Inflammation has been shown to be associated with various arrhythmias including supraventricular tachycardias (SVTs). In this study, we aimed to investigate the relation between NLR and SVT in patients with a documented atrial tachyarrhythmia.

METHODS

The study used a retrospective cross-sectional design. Patients who had SVT but were otherwise healthy were included. The exclusion criteria included drug use (except antiarrhythmic agents), morbid obesity, acute or chronic infection, inflammatory diseases, systemic diseases, and cancer. Total and differential leukocyte counts and routine biochemical tests were performed before the ablation procedure.

RESULTS

The study included 150 patients with SVT and 98 healthy controls. The biochemical and hematological parameters were comparable between the groups, except neutrophil and lymphocyte counts. The neutrophil count was significantly higher (4.7±1.5x103/µL versus 4.1±1.0x103/µL; p<0.001) and lymphocyte count was significantly lower (2.2±0.6x103/µL versus 2.5±0.6x103/µL; p=0.001) in the SVT group than in the control group. As a result, the SVT group had significantly higher NLR values than the control group (2.2±0.9 versus 1.7±0.5; p<0.001). In addition, NLR values were higher in patients in whom tachycardia was induced during an electrophysiological study (EPS) (2.3±0.9 versus 2.0±0.8; p=0.02). The association between NLR and SVT remained significant after multivariate analysis (odds ratio: 1.5, 95% confidence interval: 1.001-2.263, p=0.049).

CONCLUSION

Our study indicated that NLR values were significantly higher in patients with documented SVT than in control subjects. Inducibility of SVT during EPS was associated with higher NLR values.

The importance of the mean platelet volume in the diagnosis of supraventricular tachycardia

BACKGROUND

This retrospective study aimed to investigate the diagnostic relation between the mean platelet volume (MPV) and supraventricular tachyarrhythmia (SVT) in patient with documented atrial tachyarrhythmia in the emergency department (ED).

METHODS

Two study groups were compared; a SVT group with arrive at the ED with documented SVT (n=122) and 100 healthy adult without any palpitation symptom, arrhythmic disease, and with normal physical examination results that were brought for checkups to the cardiology polyclinic were classified as control group. Blood samples were obtained from all patients for determining the hematologic counts and MPV during first hour in ED period.

RESULTS

In terms of the focus of the study, hemoglobin, neutrophil count, mean cell volume (MCV), red cell distribution width (RDW), platelet, white blood cell (WBC), and lymphocyte counts were similar in both group (p>0.05). MPV in the SVT group was significantly higher than in the control group (9.12 ± 1.22 flvs 8.64 ± 0.89 fl, p<0.001). Multivariate logistic regression analysis showed that just MPV was independent predictor of SVT in patients with palpitation in ED (odds ratio [OR] 8.497, 95% confidence interval (6.181 to 12.325), p=0.012).

CONCLUSION

The present study described that MPV is helpful parameter for the diagnosis of SVT in emergency department, for the first time in the literature.

The diagnostic significance of NT-proBNP and troponin I in emergency department patients presenting with palpitations

OBJECTIVE

This prospective study investigated the diagnostic significance of the N-terminal pro-brain natriuretic (NT-proBNP) and troponin I peptides in emergency department patients presenting with palpitations.

METHODS

Two groups of patients with palpitations but without documented supraventricular tachycardia were compared: a group with supraventricular tachycardia (n = 49) and a control group (n = 47). Both groups were diagnosed using electrophysiological studies during the study period. Blood samples were obtained from all of the patients to determine the NT-proBNP and troponin I levels within the first hour following arrival in the emergency department.

RESULT

The mean NT-proBNP levels were 207.74±197.11 in supraventricular tachyarrhythmia group and 39.99±32.83 pg/mL in control group (p<0.001). To predict supraventricular tachycardia, the optimum NT-proBNP threshold was 61.15 pg/mL, as defined by the receiver operating characteristic (ROC) curve, with a non-significant area under the ROC curve of 0.920 (95% CI, 0.86-0.97, p<0.001). The NT-proBNP cut-off for diagnosing supraventricular tachycardia had 81.6% sensitivity and 91.5% specificity. Supraventricular tachycardia was significantly more frequent in the patients with NT-proBNP levels ≥61.15 pg/mL (n = 44, 90.9%, p>0.001). The mean troponin I levels were 0.17±0.56 and 0.01±0.06 pg/mL for the patients with and without supraventricular tachycardia, respectively (p<0.05). Of the 96 patients, 21 (21.87%) had troponin I levels ≥0.01: 2 (4.25%) in the control group and 19 (38.77%) in the supraventricular tachycardia group (p<0.001).

CONCLUSION

Troponin I and, in particular, NT-proBNP peptide were helpful for differentiating supraventricular tachycardia from non- supraventricular tachycardia palpitations. Further randomized, large, multicenter trials are needed to define the benefit and diagnostic role of NT-proBNP and troponin I in the management algorithm of patients presenting with palpitations in emergency departments.

[ST-segment depression and elevation during supraventricular tachycardias]

Three electrocardiograms with repolarisation abnormalities (ST-segment depression and elevation) during supraventricular tachycardias are presented. In all three cases the subjects were young and otherwise healthy. Despite this in one of these cases an acute coronary syndrome was erroneously diagnosed on the basis of pronounced ST-segment depression in several leads and troponin I elevation. Coronary angiogram and echocardiogram in this case was normal. Diagnostic value and aetiology of repolarisation abnormalities during supraventricular tachycardias are discussed.

Severe toxicity following synthetic cannabinoid ingestion

OBJECTIVE

To report a case of seizures and supraventricular tachycardia (SVT) following confirmed synthetic cannabinoid ingestion.

BACKGROUND

Despite widespread use of legal synthetic cannabinoids, reports of serious toxicity following confirmed use of synthetic cannabinoids are rare. We report severe toxicity including seizures following intentional ingestion of the synthetic cannabinoid JWH-018 and detail confirmation by laboratory analysis.

CASE REPORT

A healthy 48 year old man had a generalized seizure within thirty minutes of ingesting an ethanol mixture containing a white powder he purchased from the Internet in an attempt to get high. Seizures recurred and abated with lorazepam. Initial vital signs were: pulse, 106/min; BP, 140/88 mmHg; respirations, 22/min; temperature, 37.7 °C. A noncontrast computed tomography of the brain and EEG were negative, and serum chemistry values were normal. The blood ethanol concentration was 3.8 mg/dL and the CPK 2,649 U/L. Urine drug screening by EMIT was negative for common drugs of abuse, including tetrahydrocannabinol. On hospital day 1, he developed medically refractory SVT. The patient had no further complications and was discharged in his normal state of health 10 days after admission. The original powder was confirmed by gas chromatography mass spectrometry to be JWH-018, and a primary JWH-018 metabolite was detected in the patient's urine (200 nM) using liquid chromatography tandem mass spectrometry.

DISCUSSION

Synthetic cannabinoids are legal in many parts of the world and easily obtained over the Internet. Data on human toxicity are limited and real-time confirmatory testing is unavailable to clinicians. The potential for toxicity exists for users mistakenly associating the dose and side effect profiles of synthetic cannabinoids to those of marijuana.

CONCLUSION

Ingestion of JWH-018 can produce seizures and tachyarrhythmias. Clinicians, lawmakers, and the general public need to be aware of the potential for toxicity associated with synthetic cannabinoid use.

Relationship of myocardial ischemia and injury to coronary artery disease in patients with supraventricular tachycardia

Increase of serum troponin I and ST-segment depression are objective markers of myocardial ischemia/injury. Abnormalities of the 2 indicators have been associated with supraventricular tachycardia (SVT) but their relevance for diagnosing acute coronary syndrome and the presence of coronary artery disease (CAD) in this setting have not been clarified. Therefore, we sought to evaluate the frequency of CAD based on increased troponin I and ST-segment depression during SVT. During a 5-year period, 104 patients were admitted with a diagnosis of SVT, 80 of whom had troponin I testing, and 70 of these patients could be assessed for ST-segment changes. Thirty-seven patients (48%) had increased troponin I (mean 1.54 +/- 2.7 ng/dl, normal <or=0.07 ng/dl) and 46 patients (57%) had ST-segment depression >or=1.0 mm. There were no significant differences in baseline characteristics and clinical presentation of patients with and without troponin I increase or ST-segment depression. There was no difference in the diagnosis of CAD by noninvasive or invasive testing in patients with and without increased troponin I. More patients with than without ST-segment depression had evidence of CAD (22% vs none, p = 0.01), but after adjusting for covariates, ST-segment depression was not a significant predictor of CAD. In conclusion, increased troponin I and ST-segment depression are not significant markers of acute coronary syndrome in patients with SVT.

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.

Patients with paroxysmal atrial fibrillation but not paroxysmal supraventricular tachycardia display evidence of platelet activation during arrhythmia

It is well known that chronic atrial fibrillation (CAF) and paroxysmal atrial fibrillation (PAF) are associated with hypercoagulable state. However, pathological hemostatic changes during the paroxysmal supraventricular tachycardia (PSVT) have not yet been elucidated. To determine platelet activity in patients with PSVT, PAF and CAF, we examined the levels of beta-thromboglobulin (BTG) and platelet factor 4 (PF4) during tachyarrhythmia attacks. We measured the levels of BTG and PF4, as an index of platelet activation in 15 patients with PAF (9 men, mean age 45+/-11), and 14 patients with PSVT (8 men, mean age 40+/-10). Levels were compared to 22 age and sex matched healthy controls in sinus rhythm and with 25 patients with CAF (16 men, mean age 51+/-12). Blood samples were taken during arrhythmia and 24 hours after conversion to sinus rhythm. Patients taking medications or have clinical conditions that may affect the BTG and PF4 levels were excluded. In patients with PAF, BTG and PF4 levels were significantly higher than in controls (p<0.009, and p=0.002, respectively), and in patients with PSVT (p<0.004, and p=0.009, respectively), however, BTG and PF4 levels were significantly lower than CAF patients (p=0.002, and p=0.02, respectively). Moreover, BTG and PF4 levels were significantly decreased 24 hours after conversion to sinus rhythm (p<0.0001), and p=0.004, respectively). Although BTG and PF4 levels in patients with PSVT were significantly lower than in patients with PAF (p=0.04, and p=0.009, respectively) and CAF (p=0.0001, and p=0.0001, respectively), BTG and PF4 levels were similar to controls and did not change significantly after recovery to sinus rhythm (p=NS for all). These results indicate that there was no platelet activation in patients with PSVT during tachyarrhythmia but significantly increased platelet activity in PAF and CAF patients. There was a significant decrement of the platelet activity to a level of control subjects twenty-four hours after cardioversion of PAF.

Increased plasma levels of atrial natriuretic peptide (ANP) in patients with paroxysmal supraventricular tachyarrhythmias

Atrial natriuretic peptide (ANP) is a cardiac hormone originating from atrial cardiocytes. It seems to be involved in the regulatory control of circulating volume and vascular tone. Plasma immunoreactive atrial natriuretic peptide (IrANP) was investigated in 22 patients with paroxysmal supraventricular tachyarrhythmia (16 with atrial fibrillation, 4 with atrial flutter, one with a Wolf-Parkinson-White syndrome (WPW) and one with atrial tachycardia). During the aute attack, IrANP was significantly increased (125.3 +/- 11.4 pmol/l) compared to samples obtained during convalescence (55.9 +/- 4.7 pmol/l). Heart rate (HR) was 144 +/- 4.3 beats/min during the arrhythmia and 75 +/- 2.6 during convalescence. The reduction of IrANP in plasma from the acute attack of tachycardia to follow-up was significantly related to the reduction of HR (p less than 0.05). Irrespective of type of paroxysmal supraventricular tachyarrhythmia, 50% of the patients experienced polyuria during the attack. This symptom was more frequent in younger patients with a shorter duration of tachycardia. Polyuria patients had a higher HR during the attack of supraventricular tachycardia. Even though polyuria was not always found in the patients with the highest IrANP values, the symptom was associated with significantly higher concentrations of IrANP in plasma compared to the non-polyuria group. We conclude that IrANP is increased in plasma during acute attacks of paroxysmal supraventricular tachycardia. Furthermore, the polyuria frequently associated with this condition may partly be due to excess release of ANP from cardiac myocytes.

[The utility of assaying the N-terminal of brain natriuretic peptide precursor (NT pro-BNP) to predict the clinical outcome in patients with supraventricular tachyarrhythmias observed and treated in the emergency room]

Many patients arrive at the emergency room (ER) with recent-onset atrial fibrillation or other forms of supraventricular tachyarrhythmia (SV Ta) or tachycardia. The restoration of sinus rhythm (SR) is always desirable and, in addition, can enable many hospitalisations to be avoided, thereby achieving considerable savings in financial and healthcare resources. Even in haemodynamically stable cases, it is clearly useful to be able to evaluate which subjects will benefit most from attempts to restore SR, even when few truly diagnostic means are on hand (such as echocardiography, which is not always promptly available in the ER setting). We evaluated the brain natriuretic peptide precursor (N terminal pro-BNP) in 105 patients arriving at the ER. We observed that SR was restored in a low percentage of patients with values > 4500, while the vast majority of those with values < 1500 was normalised even by means of antiarrhythmic drugs alone. It is therefore probable that a medium-low value of the hormone indicates only an acute response to the distension of the atrial tissue induced by the arrhythmia; by contrast, decidedly elevated values are probably also caused by ventricular dysfunction and therefore indicate a lesser likelihood of restoring SR. The routine evaluation of NT pro-BNP could be used as an alternative to echocardiography in order to rapidly select patients in whom cardioversion should be attempted in the ER or Brief Observation Unit.

Serum cardiac markers response to biphasic and monophasic electrical cardioversion for supraventricular tachyarrhythmia—a randomised study

BACKGROUND

Electrical cardioversion in patients with various types of supraventricular tachyarrhythmia (SVT) may induce serum cardiac markers elevation. Only a few studies have evaluated the impact of the type of shock waveform on electrical myocardial injury. The aim of our study was to compare the response of serum cardiac markers to biphasic and monophasic cardioversion for SVT.

METHODS

One hundred and forty one patients with various SVTs referred for electrical cardioversion were randomised to monophasic (MP) or biphasic (BP) cardioversion. Serum levels of creatine kinase (CK), MB fraction of CK (CK-MB), myoglobin and troponin I were analysed before cardioversion and 254+/-58 min after the procedure.

RESULTS

Average age of the patients was 67.9+/-11.3 years, 71 underwent BP and 70 MP cardioversion. In MP group, cumulative energy (CE)>150J was associated with significant elevation of CK and myoglobin levels after cardioversion (1.52+/-3.81 microkat/l and 187+/-433 microg/l), while CE<150J was not (-0.04+/-0.34 and 4+/-11, p<0.05). In BP group, CE>150J was associated with significant but smaller CK elevation (0.27+/-1.09 microkat/l, p<0.05) and comparable myoglobin elevation (80.7+/-21.4 microg/l, p<0.05). CE>150J was the only independent positive predictor for CK and myoglobin elevation in both groups. No significant changes in CK-MB and Troponin I levels after cardioversion were identified.

CONCLUSIONS

According to our study, electrical cardioversion for SVTs is not associated with biochemical signs of myocardial injury. Application of CE>150J can be followed by CK and myoglobin elevation most likely due to skeletal muscle damage. This reaction is more pronounced in MP than in BP cardioversion.

Elevated Troponin Levels after Prolonged Supraventricular Tachycardia in Patient with Normal Coronary Angiography

The European Society of Cardiology and the American College of Cardiology redefined the concept of myocardial infarction in the presence of highly positive markers of myocardial injury associated with at least one of the following: ischemic symptoms; development of pathologic Q waves on the ECG or ECG changes indicative of ischemia (positive or negative deviation of the ST segment), making troponins one of the most important aspects in the evaluation and stratification of patients with chest pain in the emergency room. However, although troponin gives excellent accuracy in the identification of myocardial necrosis, it is known that it can also be elevated in a series of nonatherosclerotic heart diseases. We present the case of a 49-year-old female patient admitted to the Chest Pain Unit with a history of supraventricular tachycardia associated with chest discomfort, nausea and diaphoresis. During risk stratification, the patient presented with a high serum troponin T level (0.143 ng/ml) but with a normal coronary angiography.

Low serum albumin levels in patients with paroxysmal atrial fibrillation: what does it mean?

BACKGROUND

Atrial fibrillation is the most common cardiac rhythm disturbance in clinical practice; its risk factors are complex and far from being clarified up to now. Previous studies demonstrated that hypoalbuminaemia significantly correlates with cardiac diseases.

HYPOTHESIS

We hypothesized that the serum albumin levels were decreased in patients with paroxysmal atrial fibrillation (PAF) and that hypoalbuminaemia was a risk factor for PAF.

METHODS

We selected retrospectively 32 consecutive PAF patients as experimental group and 32 strictly age- and sex-matched paroxysmal supraventricular tachycardia patients confirmed by electrophysiology as a normal control group. Serum albumin was assayed by the bromocresol green (BCG) method. The experimental group was compared with the control group using the paired sample t test for independent samples when dealing with approximately normally distributed variables and the Wilcoxon rank-sum test when appropriate. One sample t test was used to compare albumin levels of the control group with the normal population mean value established in this laboratory so as to eliminate the selection bias. The correlations between albumin levels and cardiac function classifications (NYHA) were assessed using Spearman's rho. Categorical variables were compared using chi-squared, Fisher's exact test or RxC contingency table. Logistic regression was used for analysis of risk factors of serum albumin levels and PAF.

RESULTS

The baseline clinical characteristics between the 2 groups were comparable with no significant difference. In a univiariate analysis, albumin was significantly lower in patients with PAF (41.67 +/- 3.52 g/L) than in control patients (43.88 +/- 3.53 g/L, P = 0.009). The albumin levels among patients in the presence and the absence of baseline factors showed insignificant difference (P > 0.05). In a multivariable analysis of covariance that considered baseline factors, only PAF was an independent predictor of decreased albumin levels (P = 0.0454, OR = 0.375). Conversely, only hypoalbuminaemia was an independent predictor of PAF (P = 0.0129, OR = 0.773).

CONCLUSIONS

PAF is associated with hypoalbuminaemia and hypoalbuminaemia is an independent risk factor for PAF patients. Although the cause and effect of hypoalbuminaemia and PAF remains to be clarified, the present study provides new information with respect to the aetiology and therapy of PAF patients.

Adenosine cardioprotection study in clinical setting of paroxysmal supraventricular tachycardia

PSVT attack of >20min and frequency >160 is well-recognized model of myocardial dysfunction. We measured 6-keto-PGF1alpha and TXB(2) before and after adenosine administration to assess its cardioprotective potential. A total of 64 patients were randomly assigned as having acute episode of PSVT to adenosine or verapamil group. A bolus of 6mg of adenosine up to the maximum dose of 12 or 5mg of verapamil up to the maximum dose of 10mg were given, until the sinus rhythm was restored. The levels of PGI(2), TXA(2) and TAS were measured in three different time intervals. In adenosine group all parameters were normalized after 20min of conversion to sinus rhythm. The ratio of PGI(2)/TXA(2) increased after 5min of conversion to SR (P<0.01). Also, the ratio of TXA(2)/TAS was decreased for ADO (P<0.01). This is the first study to demonstrate that adenosine exerts cardioprotective effect.

Blood oxygen saturation during atrio-ventricular dissociation with wide-QRS complex tachycardias

Amplitude ratios of two adjacent mixed blood oxygen saturation curve peaks in randomly selected strips of ECG were analysed in 32 patients with regular wide-QRS complex tachycardias and 60 control subjects where pacing was performed before ablation of narrow-QRS complex tachycardias. Patients with VT showed different patterns of A-to-V relationships, leading to varying ratios of SpO2 adjacent peak amplitudes, in contrast to patients with aberrant SVTs and 1:1 AV association. Application of a criterion of adjacent SpO2 peaks differing by twofold or more had a sensitivity of 90.0% and specificity of 83.3% to detect AV dissociation during VT. Fluctuations on the mixed oxygen saturation curve may be a useful non-invasive clinical parameter to detect different ventricular filling caused by atrio-ventricular dissociation during VT.

Effect of heparin on activation of platelet function in patients during radiofrequency catheter ablation

1. Thromboembolism occurs in 0.4-2.0% of patients undergoing radiofrequency catheter ablation (RFCA). Some studies have shown that treatment with heparin inhibits the activation of coagulation and fibrinolysis. No study has directly measured the activation of platelet aggregation to investigate the effect of heparin on platelet function. The purpose of the present study was to observe the inhibitory effect of heparin on platelet activity in patients undergoing RFCA. 2. Sixty-two patients with supraventricular tachycardia were observed and divided into a heparin-treatment group and a control group. Changes in platelet aggregability (PAG) and thromboxane B(2) (TXB(2)) in the blood samples of all patients at different times (before, after electrophysiological study, immediately after and 10 and 30 min after the RFCA procedure) were observed. 3. No indication of clinically symptomatic thromboembolism and no major differences in baseline characteristics and procedure were apparent in either group. The levels of PAG and TXB(2) were all clearly increased after the electrophysiological study (all P < 0.05). Immediately after RFCA, PAG and TXB(2) levels were significantly increased in both groups and remained elevated 30 min after the procedure (all P < 0.05). In the heparin-treatment group, the increases in PAG (54.69 +/- 3.24%) and TXB(2) (29.01 +/- 1.84%) caused by RFCA were lower than changes observed in the control group (70.92 +/- 3.45 and 44.70 +/- 3.28%, respectively; both P < 0.01). Moreover, treatment with heparin normalized the elevated level of PAG 30 min after RFCA more clearly. 4. The results of the present study suggest that intravenous heparin treatment during the operation inhibits the activation of platelets induced by RFCA.

[Supraventricular tachycardia as a cause of elevated troponin I in a patient with normal coronary arteries]

The authors describe otherwise healthy 69-year-old man admitted to the hospital with supraventricular tachycardia (193/min) accompanied by chest pain and marked ST depression on ECG. Sinus rhythm was restored after verapamil (5 mg i.v.) administration. Symptoms resolved and ECG returned to normal. However, elevation of troponin I level (1.2 ng/ml) was observed a few hours later. Echocardiography as well as coronary angiogram were normal. In electrophysiologic study typical AVNRT was diagnosed and successful ablation of the slow pathway was performed. The authors present a review of current literature on myocardial ischaemia due to supraventricular tachycardia despite normal coronary arteries. In conclusion authors suggest that elevated troponin levels may reflect subendocardial ischaemia and should prompt RF ablation of underlying arrhythmia.

Effect of Radiofrequency Catheter Ablation on Plasma B‐type Natriuretic Peptide

The study was designed to investigate the impact of radiofrequency catheter ablation on the plasma level of B-type natriuretic peptide (BNP). In 36 patients who underwent catheter ablation of paroxysmal supraventricular tachycardia, the plasma level of BNP was analyzed before and after the ablation procedures. The plasma BNP at baseline, 30 minutes after the ablation, 3 and 24 hours after the ablation was 12.78 +/- 2.47, 18.45 +/- 4.02 (P = 0.446), 43.54 +/- 8.12 (P = 0.0001), and 17.88 +/- 4.71 (P = 0.493) pg/mL, respectively. Plasma troponin I was also increased 3 and 24 hours after the ablation (n = 10, P < 0.05). Multivariate regression analysis showed a significant correlation between the levels of BNP 3 hours after ablation and the preablation BNP and the total radiofrequency energy used for the ablation. We conclude that radiofrequency catheter ablation of supraventricular tachycardia increases the plasma level of BNP. The clinical significance of the ablation-induced increase in BNP needs to be further investigated.

[The activation of haemostasis during radiofrequency catheter ablation]

The aim of the study was to investigate chosen haemostasis activation markers during electrophysiologic study (EPS) with consequent radiofrequency catheter ablation (RFA). Sixty-three patients were studied prospectively. Indications for EPS and RFA were supraventricular tachycardias with the arrhythmogenic substrate located in the right atrium. Blood samples were drawn 24 hours before the procedure (T -1), at the beginning of the procedure (T0), at the end of EPS (T1), 30 minutes after completion of RFA (T2), and 24 hours after the procedure (T3). To study coagulation, fibrinolytic and platelet activation were measured concentrations of thrombin-antithrombin III (TAT), D-dimers (DD), platelet count and parameters, and circulating platelet aggregates (CPAi). During the EPS and RFA, TAT levels increased from the baseline 5.03 +/- 2.53 microg/l (T -1) to 12.90 +/- 12.83 microg/l at T0 (p < 0.001) to 36.07 +/- 15.59 microg/l at T1 (p < 0.001) and decreased to 28.85 +/- 13.14 microg/l at T2 (p < 0.001). Levels of DD increased from 0.30 +/- 0.20 mg/l at T0 to 0.44 +/- 0.25 mg/l at T1 (p < 0.001) and to 0.87 +/- 0.74 mg/l at T2 (p < 0.001). The number of platelets was significantly decreased (-13.7%) before and during the procedure (T -1 vs. T3; p < 0.001). Marked platelet activation (CPAi 0.62 +/- 0.32) was observed before the procedure opposite to the physiological values (CPAi 1.0 +/- 0.1), without changes during the procedure (CPAi at T2 0.69 +/- 0.23). Our results confirmed activation of several haemostasis parameters during EPS and RFA, and support eligibility of the antithrombotic prevention in patients indicated for EPS and RFA.

Elevated troponin levels in absence of coronary artery disease after supraventricular tachycardia

Generally speaking elevated troponin levels are consistent with the diagnosis of acute coronary syndrome and haemodynamically relevant coronary artery stenosis. However, they may also point to minor myocardial injury in other circumstances. Four patients with elevated troponin levels after supraventricular tachycardia without evidence of coronary artery disease and very low risk scores for acute coronary syndrome are described and discussed.

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.

Population pharmacokinetics and pharmacodynamics of sotalol in pediatric patients with supraventricular or ventricular tachyarrhythmia

AIMS

To derive useful pharmacokinetic (PK) and pharmacodynamic (PD) information for guiding the clinical use of sotalol in pediatric patients with supraventricular (SVT) or ventricular tachyarrhythmia (VT).

METHODS

Two studies were conducted in-patients with SVT or VT in the age range between birth and 12 years old. Both studies used an extemporaneously compounded formulation prepared from sotalol HCl tablets. In the PK study, following a single dose of 30 mg/m2 sotalol, extensive blood samples (n = 10) were taken. The PK-PD study used a dose escalation design with doses of 10, 30, and 70 mg/m2, each administered three times at 8-hr intervals without a washout. Six ECG recordings for determination of QT and RR were obtained prior to the initial dose of sotalol. Four blood samples were collected six ECG's were determined during the third interval at each dose level. Plasma concentrations of sotalol (C) were assayed by LC/MS/MS. The data analysis used NONMEM to obtain the population PK and PD parameter estimates. The individual PK and PD parameters were estimated with empirical Bayes methodology.

RESULTS

A total of 611 C from 58 patients, 477 QTc and 499 RR measurements from 23 and 22 patients, respectively, were available for analysis. The PK of sotalol was best described by a linear two-compartment model. Oral clearance (CL/F) and volume of central compartment (Vc/F) were linearly correlated with body surface area (BSA), body weight or age. CL/F was also linearly correlated with creatinine clearance. The best predictor for both CL/F and Vc/F was BSA. The remaining intersubject coefficients of variation (CV's) in CL/F, and Vc/F were 21.6% and 20.3%, respectively. The relationship of QTc to C was adequately described by a linear model. The intersubject CV's in slope (SL) and intercept (E0) were 56.2 and 4.7%, respectively. The relationship of RR to C was also adequately described by a linear model in which the baseline RR and SL were related to age or BSA. The intersubject CV's for SL and E0 were 86.7 and 14.4%, respectively.

CONCLUSIONS

BSA is the best predictor for the PK of sotalol. Both QTc and RR effects are linearly related to C. No covariates are found for the QTc-C relation, while the RR-C relation shows age or BSA dependency.

A population pharmacokinetic-pharmacodynamic analysis and model validation of azimilide

BACKGROUND

Pharmacokinetic (PK) and pharmacodynamic (PD) models for azimilide were developed and validated with sparse blood sampling and QTc interval data obtained during three clinical trials of azimilide for prevention of supraventricular arrhythmia recurrence.

METHODS

Patients were orally administered placebo or azimilide dihydrochloride, 35, 50, 75, 100, or 125 mg/d, for 6 to 9 months. NONMEM was used for data fitting and assessment of selected patient covariates and concomitant medication classes for PK/PD relationships.

RESULTS

Results indicate that azimilide clearance (CL) was dependent on body weight (WTKG), gender, and current tobacco use, where CL (L/h) = 3.92 x (WTKG - 43)(0.208), with a 17% increase for male subjects and a 15.5% increase for current tobacco use. Volume of distribution (V) was also dependent on WTKG and total bilirubin (BIL), where V (L) = 9.88 x (WTKG - 43) + 717 x (BIL)(0.348). The PK/PD analysis indicated that the baseline QTc interval was dependent on gender, New York Heart Association Class, digoxin, and paced artificial pacemaker spike, whereas the 50% effective concentration (EC(50)) was dependent on the serum potassium (K) level, where EC(50) = 107 x K. The change in EC(50) was not clinically significant within the normal range for potassium. The mean E(max) (maximum increase in the QTc interval for the E(max) models) was a 61.7 ms increase from baseline. At 125 mg/d the predicted percent increase in the QTc interval at the maximum plasma drug concentration at steady state was 9% and 10% for male and female patients, respectively. The values of the median prediction error were -3% and -0.4% for the PK and PK/PD models, respectively, and the values of the absolute prediction error were 21% and 4% for the PK and PK/PD models, respectively, indicating that both models are essentially unbiased and acceptably accurate.

CONCLUSIONS

Azimilide PK parameters are dependent on body weight, gender, smoking status, and bilirubin and are independent of the coadministration of digoxin, warfarin, and cytochrome P4503A4 inhibitors and inducers. The relationship between azimilide concentration and change in QTc is primarily dependent on serum potassium.

Troponin I elevation after supraventricular tachycardia in a child with hypertrophic cardiomyopathy

An 11-year-old patient with diagnosis of hypertrophic cardiomyopathy (HCM) developed marked elevation of troponin I in the absence of electrocardiographic signs of ischemia after two episodes of supraventricular tachycardia. At follow-up the level of troponin I returned to normal. The role of troponin I in patients with HCM as a risk marker deserves further evaluation.

Cycling of inducibility of paroxysmal supraventricular tachycardia in women and its implications for timing of electrophysiologic procedures

Arrhythmias in women may be affected by phases of the menstrual cycle. This study was designed to determine the prevalence of perimenstrual clustering of spontaneous episodes of paroxysmal supraventricular tachycardia (SVT) in women. It also tested the hypothesis that women with this temporal pattern of events have an altered probability of induction of paroxysmal SVT during electrophysiologic testing at higher estrogen states (midcycle or with estrogen replacement therapy) than at low estrogen states (perimenstrual or without estrogen replacement). A structured history of the relation of spontaneous paroxysmal SVTs to phases of the menstrual cycle was obtained prospectively among 42 women referred during a 3-year period. Patients with cyclical patterns of spontaneous tachycardias, who had had negative electrophysiologic studies at midcycle or while receiving estrogen replacement therapy, had repeat procedures (1) when premenstrual or at the onset of menses, or (2) after stopping estrogen replacement therapy. Seventeen of 42 consecutive female patients (40%) had histories of perimenstrual clustering of arrhythmias. Six women (4 with normal menstrual cycles, 2 on estrogen replacement therapy), who qualified for paired electrophysiologic studies because of a negative initial electrophysiologic study that included provocation with isoproterenol, had inducibility into SVTs during the second study. All 6 had dual atrioventricular (AV) nodal pathway physiology, 4 had AV nodal reentrant tachycardia (AVNRT) induced, 1 had both AVNRT and reciprocating AV tachycardias, and 1 had nonsustained AVNRT and an atrial tachycardia induced. Successful ablation procedures were performed in 5 of the 6 patients. Thus, among women with a history of perimenstrual clustering of paroxysmal SVT and among those receiving estrogen replacement therapy, scheduling of elective electrophysiologic procedures at times of low estrogen levels (premenstrual or off estrogen replacement therapy) may facilitate the probability of a successful procedure.

[The functional characteristics of the prostanoid system in patients with supraventricular paroxysmal tachyarrhythmias in ischemic heart disease and the pre-excitation syndrome]

Different variants of the prostanoid system response under paroxysms of tachycardia in patients with ischemic heart disease presenting with preexcitation syndrome are believed to be not only a manifestation of etiological and pathogenetic differences--they also reflect particular features of the state of the neurohumoral control on the whole in the nosological forms studied.

Electrophysiologic and hemodynamic effects of a single oral dose of pilsicainide hydrochloride, a new class 1c antiarrhythmic agent

To establish the clinical efficacy of pilsicainide, we evaluated its electrophysiologic and hemodynamic effects after a single oral administration to 18 patients with documented supraventricular tachycardia (SVT). To determine the minimal effective blood level, changes in efficacy with time were evaluated by serial reinduction studies with venous blood sampling for measurement of the plasma pilsicainide level. Sixty minutes after administration of a single oral dose of pilsicainide, the sinoatrial conduction time, AH and HV intervals, and the effective refractory period of the right ventricle were prolonged. Ventriculoatrial conduction was blocked in 11 patients [nine of 12 via accessory pathway and two of six via the atrioventricular (AV) node], resulting in the suppression of SVT induction in nine of 13 patients. Pilsicainide increased the heart rate and mean pulmonary arterial pressure and decreased the stroke volume index at 60 min. PQ interval, QRS width, and QTc were significantly prolonged after pilsicainide, and the percentage prolongations of the PQ interval were well correlated with the plasma pilsicainide levels. The plasma level effective for suppression of SVT was considered to be >0.5 microg/ml. We concluded that a single oral administration of pilsicainide is well tolerated and effective in suppressing SVT.

Clinical and electrophysiologic effects of dofetilide in patients with supraventricular tachyarrhythmias

The clinical and electrophysiologic effect of intravenous dofetilide was evaluated in patients with paroxysmal atrial fibrillation (AF) of recent onset (< 7 days) and paroxysmal supraventricular tachycardia (PSVT). From 2.5 to 5.0 micrograms/kg of dofetilide was administered intravenously for the termination of arrhythmias. For the electrophysiologic study (EPS), 3.0 micrograms for loading and subsequently 2 micrograms/kg was injected for 45 min as a maintenance dose. The EPSs were performed before the loading and during the maintenance dose. AF was successfully converted to sinus rhythm in seven (54%) of 13 patients. The duration of AF from its onset was significantly shorter in responders than that of nonresponders (p < 0.05). Dofetilide also terminated PSVT in four of six patients. In the EPS, dofetilide proportionately lengthened the effective refractory period of the atrium, ventricle, and the accessory pathways without slowing of the intracardiac conduction. Dofetilide completely suppressed the induction of PSVT in seven of 13 patients, restricted the induction zone in five, and inhibited perpetuation of the arrhythmia in the remaining one. The cycle length of PSVT remained unchanged after dofetilide. These results imply that the suppression of the development and maintenance of reentrant arrhythmias may result from the lengthening effect of dofetilide on the refractoriness and the consequent elimination of the excitable gap at the critical part of the reentrant loop.

Fibrinogen and fibrin D-dimer levels in paroxysmal atrial fibrillation: evidence for intermediate elevated levels of intravascular thrombogenesis

Because abnormalities in hemostatic factors may in part account for the risk of stroke and thromboembolism in atrial fibrillation, we measured plasma fibrinogen and fibrin D-dimer levels in 33 patients (18 men and 15 women, mean age 60.8 +/- 1.4 years [mean +/- SEM]) with paroxysmal atrial fibrillation (PAF) and 12 patients (3 men and 9 women, mean age 51.0 +/- 4.2 years) with paroxysmal supraventricular tachycardia (PSVT). Levels of these markers were compared to levels in (1) patients with chronic atrial fibrillation; (2) hospital controls (age-matched [age +/- 5 years] and sex-matched patients in sinus rhythm with coronary artery disease and normal left ventricular function); and (3) healthy population controls in sinus rhythm. Patients with PAF had intermediate levels of median plasma fibrinogen and fibrin D-dimer when compared to patients with chronic atrial fibrillation and controls in sinus rhythm (both p < 0.001). There was no relation with atrial size or ventricular function on echocardiography. Patients with PSVT had plasma fibrinogen and fibrin D-dimer levels that were similar to the median levels of the population controls, suggesting that there was no excess in thrombogenesis. These findings are consistent with the hypothesis that atrial fibrillation is related to the increases in plasma fibrinogen and fibrin D-dimer levels. Patients with PAF have intermediate levels of these markers, a finding that is consistent with the intermediate risk of thromboembolism in such patients.

Cyclical variation in paroxysmal supraventricular tachycardia in women

BACKGROUND

Paroxysmal supraventricular tachycardia (SVT) in premenopausal women is often judged to be related to anxiety, and may be associated with the menstrual cycle. The aim of this study was to determine whether a cyclical variation of episodes of SVT exists and to correlate such variation with cyclical variation in plasma ovarian hormones.

METHODS

26 women (mean age 36 [SD 8] years; with paroxysmal SVT were screened; those with regular menses who experienced at least three episodes of paroxysmal SVT in two consecutive 48-hour ambulatory ECG recordings were included. 13 patients (aged 32 [6] years) met these criteria. Patients underwent 48-hour ambulatory ECG monitoring and determination of plasma concentrations of oestradiol-17 beta and progesterone on day 7, 14, 21, and 28 of their menstrual cycle.

FINDINGS

An increase in the number and duration of episodes of paroxysmal SVT was observed on day 28 as compared to day 7 of the menstrual cycle. A significant positive correlation was found between plasma progesterone and number of episodes and duration of SVT (5.6 [2.2] ng/mL; r=0.83, p=0.0004; and r=0.82, p=0.0005), while a significant inverse correlation was found between plasma oestradiol-17 beta and number of episodes and duration of SVT (155 [22] pg/mL; r=0.89, p<0.0001; and r=0.81, p=0.0007).

INTERPRETATION

Women with paroxysmal SVT and normal menses exhibit a cyclical variation in the occurrence of the arrhythmia with their menstrual cycle. There is a close correlation between the episodes of paroxysmal SVT and the plasma concentrations of ovarian hormones. These data suggest that changes in plasma levels of ovarian hormones (and their interaction) may be of importance in determining episodes of arrhythmia in such patients. The mechanisms of these effects are unknown.

[Autonomic status and neurohumoral regulation in patients with refractory tachyarrhythmia]

Results are submitted of vegetative testing as well as of studying the 24.h excretion of catecholamines, activity of cholinesterase, the levels of thyroxin, triiodothyronine and hydrocortisone in blood plasma of 120 patients with tachyarrhythmias that do not respond to antiarrhythmic drug preparations. The functional state of the vegetative nervous system in the attack-free period in the above patients was mostly determined by hyperfunction of its sympathetic subdivision in the presence of inadequate vegetative reactivity, frequently excessive, occasionally weakened, and instability of adrenergic and cholinergic influences. It is suggested that augmented secretion of the hormones studied might be of compensatory nature.

[Current clinical interest in monitoring digoxinemia]

After a short introduction about the current role of digitalis in the treatment of the supraventrical arrhythmias and about the factors that make often problematic the achievement of an optimal posology of the drug, the results relative to more recent 340 digoxinaemia determinations in patients of Policlinico in Palermo or in outpatients are presented. Just the 43.8% of the patients had a digoxinaemia value in the range considered therapeutic; just 45 patients (32.1%), out of the 140 in which the digoxinaemia had been monitored for, at least, 5 days, were in the therapeutic range at the first determination; the 47.8% of the patients were underdosed and the 38.8% of them showed higher values than the therapeutic range. Determination 5 or more days later showed digoxinaemia values in the therapeutic range in 112 patients (80%). According to the reported results, it may be presumed that the posology correction effectuated by the physician on these patients might have been driven by the digoxinaemia values, whose determination must be considered an unavoidable guide to the digitalis treatment.

The evolution of platelet aggregability in patients undergoing catheter ablation for supraventricular tachycardia with radiofrequency energy: the role of antiplatelet therapy

Forty-two consecutive patients were checked for profiles of platelet aggregability before, during, and 10 and 30 minutes after catheter ablation. They were randomized into Group A (n = 20) who accepted intravenous aspirin (in 0.015 g/kg body weight) and Group P (n = 22) who accepted only placebo treatment. Blood samples were drawn from ascending aorta (Ao) and main pulmonary artery (MPA) simultaneously at each time period. In Group P, the EC50 of substrate induced platelet aggregability decreases significantly during (for ADP, from 1.72 to 0.78 mumol/L for samples from Ao, P < 0.0001; and from 1.68 to 0.69 mumol/L for MPA, P < 0.0001; for collagen, from 2.26 to 1.34 micrograms/mL for Ao, P < 0.005, and from 2.40 to 1.64 micrograms/mL, P < 0.0001) and 10 minutes after successful ablation (for ADP, to 0.70 mumol/L for Ao, P < 0.000, and to 0.61 mumol/L for MPA, P < 0.0001; for collagen, to 1.54 micrograms/mL for Ao, P < 0.01, and to 1.63 micrograms/mL, P < 0.0001), and then returned to baseline levels 30 minutes later (all P = NS) compared with comparative baseline levels. The levels of thromboxane B2 (TXB2) had the similar evolution. The evolution of platelet aggregability profiles was not associated with total energy dose, duration of energy application, duration of procedure, impedance, and ablation site. However, there were moderate positive correlations between the TXB2 levels and tip temperatures (r = 0.56, P < 0.05 for Ao and r = 0.65, P < 0.01 for MPA). These results suggest that increased platelet aggregability can occur during and 10 minutes after radiofrequency current ablation and antiplatelet therapy can maintain "flat" response of platelet aggregability to radiofrequency energy, which may provide possible benefits in preventing the occurrence of the complication.

Pharmacokinetics of moricizine in young patients

Moricizine is a novel phenothiazine antiarrhythmic agent that depresses the activity of ectopic foci, has a low incidence of adverse effects relative to other agents, and is useful in treating pediatric atrial ectopic tachycardia. A study was conducted to determine the pharmacokinetics of moricizine in children after oral administration. Moricizine was isolated from frozen serum obtained from four male patients (ages 7, 8, 9, and 18 years) receiving the drug for supraventricular tachycardia and analyzed by high-performance liquid chromatography with ultraviolet detection according to an established protocol. Peak serum levels were between 400 and 2000 ng/mL. Elimination of moricizine did not follow simple single-compartment pharmacokinetics. In three patients we observed an increase or slower decline in blood level occurring after 4 hours. Because of the paroxysmal nature of the tachycardias, decreases in patient heart rate could not be correlated with moricizine blood level. These results suggest that the pediatric pharmacokinetics of moricizine excretion are complex and may differ from those seen in adults.

Changes of plasma endothelin and atrial natriuretic peptide during the onset and after termination of paroxysmal supraventricular tachycardia

Radioimmunoassays were used to measure the concentration changes of plasma endothelin (ET) and atrial natriuretic peptide (ANP) during the onset and after termination of paroxysmal supraventricular tachycardia (SVT). 30 cases were reviewed and comparisons with 42 normal subjects were made. There are very significant differences (P < 0.0001) in the concentration changes of both plasma ET and ANP during the onset and 30 minutes after the termination of SVT. During the onset period of SVT, the plasma ET and ANP were markedly elevated and 30 minutes after its termination they were lowered significantly, but their concentrations were still 2-fold higher than those of the control group. As the biological effects of ANP and ET are antagonistic to each other, their parallel elevation and lowering of plasma concentrations during and after the termination of SVT reveal that these 2 hormones participate in the pathophysiological process of SVT. This phenomenon is possibly one of the homeostatic regulatory functions in the organism.

Flecainide acetate for paroxysmal supraventricular tachyarrhythmias. The Flecainide Supraventricular Tachycardia Study Group

Flecainide has been shown to be effective in short-term, controlled studies for prevention of paroxysmal supraventricular tachycardia (SVT) and paroxysmal atrial fibrillation (AF). However, it is unknown whether this beneficial response is maintained during long-term chronic therapy. Forty-nine patients were studied who enrolled in double-blind, placebo-controlled, short-term studies of safety and efficacy and subsequently received long-term, open-label therapy for > or = 6 months (mean duration of therapy, 17 months). To evaluate chronic efficacy, events during long-term therapy were documented by a transtelephonic monitor for either 4 or 8 weeks, comparable to the corresponding 4- or 8-week placebo-baseline periods in the same patients. Results during chronic therapy were compared with those at baseline and after the initial (short-term) treatment period. Compared with placebo-baseline results, the number of patients free of arrhythmic attacks increased significantly for both patients with SVT (from 24% to 82%, p = 0.013, n = 17) and patients with AF (from 12% to 68%, p < 0.001, n = 25). Mean time to first attack and mean number of days between attacks also showed significant and parallel increases during the chronic efficacy period. In patients with paired short- and long-term efficacy evaluations with the same dose of flecainide, end points were maintained at equivalent levels or showed further improvement (i.e., mean rate of AF attacks decreased further with chronic therapy, p = 0.036). No proarrhythmic events, death, or myocardial infarction occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical experience with propafenone for cardiac arrhythmias in the young

Seventy-two children were treated with propafenone between 1980 and 1990. The mean age was 34 months (range 0-192). Arrhythmias included atrioventricular re-entry tachycardia in 32 patients (44%), atrial flutter in 16 (22%), atrial or junctional ectopic tachycardia in 10 (14%), atrial re-entry tachycardias in three (4%) and ventricular arrhythmias in 11 patients (16%). The efficacy of oral treatment was good in patients with atrio-ventricular re-entry tachycardia (80%), atrial flutter (71%) and atrial ectopic tachycardia (83%); it was poor in ventricular arrhythmias (40%). The mean oral dose was 13.5 mg.kg-1. day-1. Dosage and serum levels of propafenone did not differ whether the patients were treated successfully or not. No correlation between dosage and serum level was observed. Intravenous propafenone administration was only partially successful in suppressing supraventricular tachycardias (6 of 11 patients). The presence of a congenital heart defect and the time of onset of the arrhythmias had a significant influence on the efficacy of propafenone. Better results were observed in patients with normal hearts and in whom onset of arrhythmia was pre-natal (success 80%) as well as in patients with arrhythmias seen early after surgery for congenital heart defects (success 87%). Success (65%) was also observed in patients without congenital heart defects and postnatal onset of supraventricular arrhythmias. Patients with ventricular or supraventricular arrhythmias late after corrective surgery showed the poorest response (31%).

Efficacy of adenosine in terminating catecholamine-dependent supraventricular tachycardia

The purpose of this study was to determine if adenosine is equally effective in terminating catecholamine-dependent and independent supraventricular tachycardia (SVT). The effect of adenosine on termination of SVT was studied in 21 patients: 12 with atrioventricular (AV) reciprocating tachycardia, and 9 with AV node reentrant tachycardia. Group 1 comprised 13 patients who had SVT induced in the absence of exogenous catecholamines, whereas group 2 comprised 8 who needed isoproterenol (1.6 +/- 0.4 micrograms/min) for induction. There was no statistical difference between the 2 groups regarding age, weight, mean arterial pressure during sinus rhythm and SVT, cycle length of SVT, or norepinephrine and epinephrine levels during sinus rhythm and SVT. Cycle length during sinus rhythm was significantly decreased in group 2. The mean dose of adenosine needed to terminate SVT was 52 +/- 6 micrograms/kg of body weight in group 1, and 61 +/- 12 micrograms/kg in group 2 (p > 0.05). In addition to isoproterenol not altering the minimal dose of adenosine necessary to terminate SVT, there was also no correlation between the dose of adenosine (mean 55 +/- 6 micrograms/kg) of each patient, and the corresponding endogenous epinephrine (273 +/- 59 pg/ml) (r = -0.19) and norepinephrine (400 +/- 58 pg/ml) (r = 0.01) levels during SVT, or cycle length of SVT (323 +/- 9 ms) (r = -0.35). The results show that adenosine is equally effective in terminating catecholamine-dependent and independent SVT; higher adenosine doses should not be needed to manage catecholamine-dependent SVT.(ABSTRACT TRUNCATED AT 250 WORDS)

[Plasma electrolytes in patients with paroxysmal supraventricular arrhythmia]

In 50 patients treated for paroxysmal supraventricular tachycardia or paroxysmal atrial fibrillation, plasma concentrations of potassium, magnesium and calcium were determined during arrhythmia and after 20, 60, and 180 minutes from the return of sinus rhythm. For achieving normal rhythm digitalis, quinidine and isoptin were used or electrical cardioversion was performed. No patient received potassium of magnesium preparations during observation. It was found that: 1. In patients with paroxysmal supraventricular arrhythmia a significant increase of plasma potassium concentration was observed after regression of arrhythmia. The highest potassium concentration was found after 60 minutes from the return of sinus rhythm. 2. The increase of potassium concentration was higher in patients after episode of supraventricular tachycardia than atrial fibrillation. 3. In patients with short-lasting arrhythmia (up to 3 hours) the increase of potassium concentration after achieving normal rhythm was higher than in patients with longer-lasting arrhythmia. 4. In patients with supraventricular tachycardia and atrial fibrillation a significant decrease of plasma magnesium and calcium concentrations was found after restoration of sinus rhythm.

Usefulness of propafenone for supraventricular arrhythmias in infants and children

The relation between propafenone dose, serum level, electrocardiographic parameters, antiarrhythmic drug efficacy and adverse effects was studied in 47 children with symptomatic supraventricular arrhythmias aged 1 day to 10.3 years (median 2.2 months) with a mean follow-up of 14.3 months. Propafenone trough serum levels were measured using gas chromatography. Oral propafenone (mean dose 353 mg/m2/day) was effective in 41 of the 47 patients (87.2%). Serum levels did not differ between patients responding and not responding to propafenone (0.45 +/- 0.40 vs 0.36 +/- 0.41 mg/liter). PR interval and QRS complex duration increased more significantly with propafenone dose increments (p < 0.001), than with propafenone serum levels (p < 0.05). At successful treatment PR interval and QRS complex were prolonged by a mean of 19.2 and 20.5% compared with pretreatment status. Five patients exhibited unexpected marked QRS complex prolongation (50 to 200%) despite low propafenone dosage (< 300 mg/m2/day) and level ranging from 0.05 to 1.33 mg/liter. Three patients (6.1%) were suspected of being "poor" metabolizers of propafenone. Mild chronic elevation of serum liver enzymes was observed in 5 patients treated with a larger dose (mean 448 mg/m2/day, p < 0.001). No proarrhythmia was noted on serial Holter monitors. One patient with Wolff-Parkinson-White syndrome and a normal heart had cardiac arrest after aspiration. Serial monitoring of PR interval and QRS complex duration was more useful for proper dosage adjustment than propafenone serum levels. Serum liver enzymes should be closely monitored when using higher propafenone doses. Malignant proarrhythmia could not be excluded in the 1 patient with cardiac arrest.

Comparative analysis of anti-arrhythmic effect of propranolol and metoprolol in patients with supraventricular tachyarrhythmias

Eighty-seven patients with paroxysmal tachydysrhythmias were submitted to clinical and laboratory evaluation and electrophysiologic studies were performed during the 3rd, 6th and 12th months of the therapy with propranolol or metoprolol. Metoprolol did not induce any significant change in sinoatrial correct time, in sinoatrial recovery time or in corrected sinoatrial recovery time. It decreases significantly the effective and functional AV refractory periods as well as increases the effective refractory period of the additional pathway. The mechanism of tachycardia preventing an involvement of the additional pathway in retrograde direction consists in the appearance of a block in the indicated additional pathway. The results of the humoral aspects are the following: propranolol inhibits the functions of the thyroid and sexual glands both in acute tests and in tests performed during the 3rd, 6th and 12th month of therapy; metoprolol has no significant effect on the functions of the thyroid and sexual glands; apparently, it influences the cardiac conduction system and myocardium directly.

Supraventricular tachycardia, right atrial pressure, atrial natriuretic peptide and polyuria--a necessary sequence?

The release of atrial natriuretic peptide (ANP) may be stimulated by tachycardia and the evidence from human studies suggests that this is mediated by a rise in atrial pressure. However, animal experiments suggest that tachycardia can by itself increase ANP levels without increasing right atrial pressure (RAP). We report here the case of a healthy volunteer who had supraventricular tachycardia (SVT) whilst participating in a study evaluating the relationship between changes in RAP and changes in ANP. The ANP levels rose following the SVT but there was no rise in RAP, suggesting that heart rate can modulate ANP levels without changes in RAP as has been shown in animal experiments.

Clinical and electrophysiologic effects of magnesium sulfate on paroxysmal supraventricular tachycardia and comparison with adenosine triphosphate

Electrophysiologic studies have shown that intravenous magnesium sulfate prolongs atrioventricular (AV) nodal conduction and refractoriness and thus could play a role in the management of patients with paroxysmal AV reentrant supraventricular tachycardia (SVT). The present study evaluates the clinical and electrophysiologic effects of intravenous magnesium sulfate in patients with SVT and compares them with those of adenosine triphosphate (ATP), one of the most potent drugs in the treatment of this arrhythmia. Patients with inducible sustained SVT were treated with ATP (10 or 20 mg) and magnesium sulfate (2 g over 15 seconds) during electrophysiologic study. If the tachycardia failed to terminate by the sixth minute, an additional 2 g dose of magnesium was given. ATP (10 or 20 mg) was significantly better than magnesium for terminating induced tachycardias (14 of 14 vs 6 of 14, p less than 0.0001). Arrhythmia termination with ATP was due to anterograde AV nodal blockade in all but 1 patient who developed retrograde block over an accessory pathway with decremental conduction. Arrhythmia termination by magnesium was due to retrograde block over an accessory pathway in 3 patients (including the patient with accessory pathway exhibiting decremental conduction), anterograde AV nodal conduction block in 2 patients and premature ventricular complexes in 1 patient. During induced tachycardias, only AH intervals were prolonged by ATP, whereas magnesium significantly prolonged AH and QRS intervals. Short-lasting side effects (chest pain, flushing, nausea) occurred after both drugs were administered but were more severe after magnesium.(ABSTRACT TRUNCATED AT 250 WORDS)