Comparison of Isoproterenol and Exercise Tests in Asymptomatic Subjects with Wolff-Parkinson-White Syndrome

In order to evaluate the effects of increases of sympathetic tone in ventricular response during atrial fibrillation and in the relationship between the accessory pathway effective refractory period (ERP) and ventricular rate during atrial fibrillation, 20 male subjects, aged 19 +/- 6 years, were studied electrophysiologically in basal conditions, after isoproterenol infusion (2-4 micrograms/min) and during submaximal bicycle exercise test, at a constant workload equal to that which increases the sinus rate to the same extent (140 beats/min) induced by isoproterenol infusion. Accessory pathway ERP was evaluated at the same driven rate (150 beats/min) in both instances. In the control study as during both tests atrial fibrillation paroxysms were induced by burst stimulation. In control conditions the rate increase from 100 to 150 beats/min induced a reduction of accessory pathway ERP from 266 +/- 27 msec to 244 +/- 22 msec (P less than 0.005). At the same driven rate of 150 beats/min, isoproterenol infusion and exercise test induced a more marked shortening of accessory pathway ERP to 211 +/- 28 msec (P less than 0.005) and to 214 +/- 29 msec (P less than 0.005), respectively. Atrial fibrillation paroxysms lasting more than 10 seconds were induced in 20/20 cases in the control study, in 15/20 during isoproterenol infusion and in 13/19 cases during exercise test. The shortest cycle length during atrial fibrillation was reduced from a basal value of 253 +/- 72 msec to 204 +/- 27 msec (P less than 0.05) during isoproterenol infusion and to 236 +/- 32 msec (NS) during exercise test.(ABSTRACT TRUNCATED AT 250 WORDS)     

Patient Selection for Biventricular Pacing

Biventricular Pacing. Introduction: Biventricular pacing improves functional status in the majority of patients with drug‐refractory heart failure, dilated cardiomyopathy, and interventricular conduction delay. The aim of this study was to analyze the baseline clinical and functional data of a cohort of patients implanted with a biventricular stimulation system in a single‐center experience, to verify if the pathophysiologic characteristics of patients affect outcome, and to determine if preliminary identification of the right candidates for the new therapy is possible with noninvasive parameters. Methods and Results: Since March 1999, 52 patients with advanced heart failure (idiopathic cardiomyopathy 50%, ischemic cardiomyopathy 35%, other etiology 15%) and left bundle branch block underwent cardiac resynchronization and were followed prospectively. Paired analysis over mean (± SD) follow‐up of 348 ± 154 days showed an overall significant decrease of QRS width (baseline 194 ± 33.2 msec vs follow‐up 159.6 ± 20.1 msec), New York Heart Association (NYHA) functional class (baseline 3.2 ± 0.5 vs follow‐up 2.3 ± 0.5), quality‐of‐life score (baseline 54 ± 25 vs follow‐up 25 ± 16), and increase of maximal VO₂ (baseline 12.6 ± 2.5 mL/kg/min vs follow‐up 15.0 ± 3.3 mL/kg/min). There were 80% responders (documented, persistent decrease ≥1 NYHA class) and 20% nonresponders (same NYHA class or decline of status; need for heart transplant; death due to progressive pump failure). No significant differences in baseline clinical and functional variables between the two subgroups were observed. In responders, there was a highly significant global improvement of all variables; in nonresponders, no parameters changed between baseline and follow‐up. Conclusion: These data confirm the role of biventricular pacing in improving the functional status of the great majority of a selected patient population having advanced heart failure and left bundle branch block with wide QRS complex. Basal demographic, clinical, and functional characteristics are not helpful in preliminary selection of responders. Simple evaluation of NYHA class confirms favorable outcome (improvement of functional and hemodynamic status).     

Studies on dapsone induced haemolytic anaemia

The present study was undertaken on the hypothesis that methaemoglobin production and haemolytic anaemia following dapsone administration could be ascribed to an impairment of glucose-6-phosphate dehydrogenase-enzymatic activity. Analysis of the kinetic parameters of the G-6-PD (Vmax and KM) was performed in ten patients, normal with respect to G-6-PD, suffering from various dermatoses. It was concluded that haemolytic anaemia after dapsone therapy is not due to a functional impairment of the enzyme. The close relationship between dapsone dosage, methaemoglobin production and anaemia make reasonable the hypothesis that a toxic dapsone derivative (DDS-NHOH) could be responsible for the methaemoglobin formation and the haemolytic anaemia.     

Relevance of Echocardiographic Evaluation of Right Ventricular Function in Patients Undergoing Cardiac Resynchronization Therapy

Aims: Right ventricular (RV) dysfunction is a marker of poor prognosis in heart failure (HF) patients. It is still unclear whether RV function might influence response to cardiac resynchronization therapy (CRT).
Methods: Forty-four consecutive patients with HF, large QRS, and either intraventricular or interventricular dyssynchrony underwent echocardiographic evaluation before, 1 month after, and 6 months after CRT. Response to CRT was considered in case of significant LV reverse remodeling, defined as the occurrence of LV end-systolic volume (LVESV) reduction ≥15% at 6 months.
Results: All echocardiographic indexes of baseline RV function and dimensions were significantly more impaired in nonresponders versus responders to CRT: tricuspid annular plane systolic excursion (TAPSE 15 ± 4 mm vs 20 ± 5 mm, P = 0.001), RV systolic pulmonary artery pressure (RVSP 39 ± 14 mmHg vs 27 ± 8 mmHg, P = 0.02), RV end-diastolic area (RVEDA 23 ± 6 cm² vs 16 ± 3 cm² P < 0.001), RV end-systolic area (RVESA 16 ± 6 cm² vs 8 ± 2 cm², P = 0.001), and RV fractional area change (30 ± 12% vs 48 ± 8%, P < 0.001). All the indexes of RV function significantly correlated with the percentage of LVESV reduction after CRT. Severe RV dysfunction was defined as TAPSE ≤14 mm and the population was stratified into two groups based on baseline TAPSE ≤ or > 14 mm. As compared to those with high TAPSE (n = 30), patients with low TAPSE (n = 14) were less likely to show LV reverse remodeling after CRT (76% vs 14%, P < 0.001).
Conclusions: Our study suggests that RV function significantly affects response to CRT. Poor LV reverse remodeling occurs after CRT in patients with HF having severe RV dysfunction at baseline.     

Beneficial Effects of Biventricular Pacing in Patients with a "Narrow" QRS

GASPARINI, M., et al .: Beneficial Effects of Biventricular Pacing in Patients with a "Narrow" QRS. Congestive heart failure (CHF) patients with LBBB and QRS duration >150 ms are considered the best candidates to biventricular pacing (Biv-P). However, patients with a narrow (120–150 ms) QRS may also benefit from Biv-P since true ventricular dyssynchrony may be underestimated by considering only QRS enlargement. From October 1999 to April 2002, 158 CHF patients (121 men, mean age 65 years, mean LVEF 0.29, mean QRS width 174 ms) underwent successful Biv-P implantation and were then followed for a mean time of 11.2 months. According to basal QRS duration, patients were divided in two groups, with wide QRS (≥150 ms, 128 patients, 81%) and with narrow QRS (<150 ms, 30 patients, 19%). In the wide QRS group, LVEF improved from 29% to 39% (P < 0.0001), 6-minute walk test from 311 to 463 m (P < 0.0001), while NYHA Class III–IV patients decreased from 86% to 8% (P < 0.0001). In the narrow QRS group LVEF improved from 30% to 38% (P < 0.0001), 6-minute walk test from 370 to 506 m (P < 0.0001), and NYHA Class III–IV patients decreased from 60% to 0% (P < 0.0001). The data showed that in wide and narrow QRS patients, Biv-P significantly improved clinical parameters (NYHA class, 6-minute walk test, quality-of-life, and hospitalization rate) and main echocardiographic indicators. Furthermore, narrow QRS patients had a better survival rate, rapidly regained left ventricular function, and only a few patients remained in a higher NYHA class during follow-up. These patients should not be excluded "a priori" from cardiac resynchronization therapy. (PACE 2003; 26[Pt. II]:169–174)     

Absorption pharmacokinetics of clonidine nasal drops in children

Background:  The α2 agonist clonidine has become a popular drug for premedication in children. Effects and pharmacokinetics after oral, rectal, and intravenous administration are well known. The aim of this study was to investigate the absorption pharmacokinetics of clonidine nasal drops in children.
Methods:  Thirteen ASA I pediatric patients received after induction of anesthesia 4 mcg·kg⁻¹ of clonidine by the nasal route. Blood samples were taken during a 12-h period and plasma levels of clonidine were analyzed by liquid chromatography–mass spectrometry. Data were calculated by a computer-aided curve-fitting program.
Results:  Plasma pharmacokinetics following administration of clonidine nasal drops showed a considerable interindividual variability and absorption was delayed and limited. A total of 95% confidence intervals for maximum plasma concentration and time to achieve maximum plasma concentration were 0.4–0.6 ng·ml⁻¹ and 1.4–3.0 h, respectively.
Conclusions:  Clonidine nasal drops are erratically absorbed from the nasal mucosa and, thus, this mode of drug administration is not recommended for premedication purposes.