Energetic metabolism during acute stretch-related atrial fibrillation.

BACKGROUND AND METHODS: Perturbations in energetic metabolism and impaired atrial contractility may play an important role in the pathogenesis of atrial fibrillation (AF). Besides, atrial stretch is commonly associated with AF. However, the atrial energetics of stretch-related AF are poorly understood. Here, we measured indicators of energy metabolism during acute stretch-related AF. PCr, adenine nucleotides, and derivatives concentrations as well as the activity of the F(0)F(1)-ATPase and Na,K-ATPase were obtained after 1 h of stretch and/or AF in isolated rabbit hearts and compared to control hearts without stretch and AF. RESULTS: After 1 h of stretch-related AF, the total adenine nucleotides' pool was significantly lower (42.2 +/- 2.6 vs. 63.7 +/- 8.3 micromol/g protein in control group, P < 0.05) and the PCr/ATP ratio significantly higher (2.3 +/- 0.3 vs. 1.1 +/- 0.1 in control group P < 0.05), because of ATP, ADP, and AMP decrease and PCr increase. The sum of high-energy phosphate compounds did not change. There were no significant differences in F(0)F(1)-ATPase nor Na,K-ATPase activity between the groups. CONCLUSIONS: Results show that in this experimental model, acute stretch-related AF induces specific modifications of atrial myocytes energetics that may play a pivotal role in the perpetuation of the arrhythmia.

Randomized comparison of simultaneous biventricular stimulation versus optimized interventricular delay in cardiac resynchronization therapy. The Resynchronization for the HemodYnamic Treatment for Heart Failure Management II implantable cardioverter defibrillator (RHYTHM II ICD) study.

BACKGROUND: The clinical value of interventricular (V-V) delay optimization in patients with chronic congestive heart failure (CHF) undergoing implantation of a device for cardiac resynchronization therapy (CRT) has not been clearly demonstrated. METHODS: RHYTHM II was a single-blind randomized trial including 121 recipients of a device for CRT with cardioverter/defibrillator capabilities (CRT-D) randomly assigned in a 1:3 ratio to simultaneous (n = 30) versus optimized (OPT) (n = 91) biventricular pacing. V-V delay was optimized by echocardiography. The study end points were (1) freedom from CRT-D system-related complications and (2) changes between preimplant and 6 months of follow-up in (a) New York Heart Association CHF functional class, (b) distance covered during a 6-minute hall walk, and (c) quality of life (QOL). RESULTS: In the OPT group, the V-V delay ranged from 0 to 80 milliseconds, with 28.4% of patients stimulated at an OPT V-V delay of 0 milliseconds. The overall 6-month survival free of adverse events requiring invasive interventions was 81.8%. In the whole cohort, 6 months of CRT-D was associated with a significant decrease in New York Heart Association class, increase in the distance covered during the 6-minute hall walk, and improvement in QOL (each P < .0001). The effects of CRT-D on these end points were similar in both study groups. CONCLUSIONS: Cardioverter-defibrillator capabilities was associated with a significant alleviation of CHF symptoms, increase in functional capacity, and improvement in QOL. The optimization of the V-V delay conferred no additional benefit compared with simultaneous biventricular stimulation.

An implantable loop recorder study of highly symptomatic vasovagal patients: the heart rhythm observed during a spontaneous syncope is identical to the recurrent syncope but not correlated with the head-up tilt test or adenosine triphosphate test.

OBJECTIVES: The aim of this study was to analyze the heart rhythm during spontaneous vasovagal syncope (VVS) in highly symptomatic patients with implantable loop recorders (ILR) and to correlate this rhythm with the heart rhythm observed during head-up tilt test (HUT). BACKGROUND: Heart rhythm obtained during provocative condition is often used to guide therapy in VVS. To date there is no conclusive evidence that the heart rhythm observed during a positive HUT can predict heart rhythm during VVS or that the heart rhythm observed during a spontaneous syncope will be identical to the recurrent syncope. METHODS: Twenty-five consecutive VVS patients (age 60.2 +/- 17.1 years; 14 women,) presenting with frequent syncopes (6.9 +/- 4.6 episodes/year) and a positive HUT (cardioinhibitory in 8 patients) were implanted with an ILR. Seven of them also had a positive adenosine triphosphate (ATP) test. RESULTS: Follow-up was 17.0 +/- 3.6 months. Thirty VVS were observed in 12 patients. Nine episodes showed bradycardia of <40 beats/min or asystole; progressive sinus bradycardia preceding sinus arrest was the most frequent electrocardiographic finding. Twenty-one syncopes occurred without severe bradycardia. The heart rhythm observed during the first syncope was identical to the recurrence. No correlation was found between slow heart rate at the ILR interrogation and a cardioinhibitory HUT response (p = 1.0) or a positive ATP test (p = 1.0). CONCLUSIONS: In highly symptomatic patients with VVS, the heart rhythm observed during spontaneous syncope does not correlate with the HUT. The heart rhythm during the first spontaneous syncope is identical to the recurrent syncope.

Diastolic asynchrony is more frequent than systolic asynchrony in dilated cardiomyopathy and is less improved by cardiac resynchronization therapy.

OBJECTIVES: To compare the incidence of diastolic and systolic asynchrony, assessed by tissue Doppler imaging (TDI), in patients with congestive heart failure (CHF) and severe left ventricular (LV) dysfunction, and to assess TDI changes induced by cardiac resynchronization therapy (CRT). BACKGROUND: Thirty percent of CRT candidates are nonresponders. Besides QRS width, the presence of echographic systolic asynchrony has been used to identify future responders. Little is known about diastolic asynchrony and its change after CRT. METHODS: Tissue Doppler imaging was performed in 116 CHF patients (LV ejection fraction 26 +/- 8%). Systolic and diastolic asynchrony was calculated using TDI recordings of right ventricular and LV walls. RESULTS: The CHF group consisted of 116 patients. Diastolic asynchrony was more frequent than systolic, concerning both intraventricular (58% vs. 47%; p = 0.0004) and interventricular (72 vs. 45%; p < 0.0001) asynchrony. Systolic and diastolic asynchrony were both present in 41% patients, but one-third had isolated diastolic asynchrony. Although diastolic delays increased with QRS duration, 42% patients with narrow QRS presented with diastolic asynchrony. Conversely, 27% patients with large QRS had no diastolic asynchrony. Forty-two patients underwent CRT. Incidence of systolic intraventricular asynchrony decreased from 71% to 33% after CRT (p < 0.0001), but diastolic asynchrony decreased only from 81% to 55% (p < 0.0002). Cardiac resynchronization therapy induced new diastolic asynchrony in eight patients. CONCLUSIONS: Diastolic asynchrony is weakly correlated with QRS duration, is more frequent than systolic asynchrony, and may be observed alone. Diastolic asynchrony is less improved by CRT than systolic. Persistent diastolic asynchrony may explain some cases of lack of improvement after CRT despite good systolic resynchronization.

Mechanism of atrial fibrillation: decremental conduction, fragmentation, and ectopic activity in patients with drug resistance paroxysmal atrial fibrillation and structurally normal heart.

Atrial fibrillation (AF) has been associated with premature beats and decreased atrial conduction velocity. This study examined a new index of dynamic inter-atrial conduction time (iaCT) in patients with paroxysmal AF (PAF). We compared 42 consecutive patients with paroxysmal AF (mean age = 52 +/- 16 years) without structural heart disease with 39 age-matched patients (mean age = 49 +/- 15 years) who underwent ablation of junctional tachycardias. Prior to investigation, all antiarrhythmic drugs were discontinued for an appropriate period of time. The following measurements were made: baseline iaCT (iaCTb) between high right atrium (HRA) and distal coronary sinus, iaCT during HRA pacing S1S1 600 ms (iaCTS1), maximum prolongation of iaCT during S2 and S3 delivery (iaCTS2, iaCTS3). We then derived the decremental index (DI), the maximum percent prolongation of iaCT = iaCT S3-iaCTS1/iaCTS1%. In patients with PAF, iaCTb was 81.3 +/- 24 ms versus 59.5 +/- 14 ms in controls (P = 0.0001). Atrial fibrillation was reproducibly and easily induced with a prominent increase in iaCT in 11 patients with AF. In this subgroup DI was 92 +/- 17%, compared to 45 +/- 21% in the other patients with AF (P = 0.0001) and 21 +/- 15% in the control group (P = 0.0001). Spontaneous isolated or repetitive ectopic activity was observed in 11 patients with AF (26%), and decremental atrial conduction was observed in 76% of patients with AF. This study supports the role of dynamic inter-atrial conduction disturbances in patients with lone PAF. The DI may be a new index of vulnerability to paroxysmal AF.

Etiologic diagnosis of 204 pericardial effusions.

The etiologic evaluation of pericardial effusion is frequently unsuccessful when noninvasive methods are used. To determine the cause of the current episode, all patients with echographically identified pericardial effusion from May 1998 to December 2002 underwent noninvasive diagnostic testing of blood, throat, and stool samples. Patients with postpericardiotomy syndrome were excluded. To analyze the value of our tests, we tested randomly selected blood donors as negative controls. Among 204 included patients, 107 (52.4%) had a final etiologic diagnosis: the etiology of 52 was highly suspected at first examination and later confirmed (thyroid deficiency, 5 cases; systemic lupus erythematous, 7; rheumatoid arthritis, 7; scleroderma, 3; cancer, 25; and renal insufficiency, 5). A definite etiologic diagnosis was made in 11 patients from pericardial fluid analysis (cancer, 5 cases; tuberculosis, 3; Streptococcus pneumoniae, Citrobacter freundii, and Actinomyces, 1 case each). Among 141 patients considered to have idiopathic pericarditis, 44 (32.1%) gained an etiologic diagnosis by our systematic testing strategy. This included serologic evaluation of serum (Coxiella burnetii, 10 cases; Bartonella quintana, 1; Legionella pneumophila, 1; Mycoplasma pneumoniae, 4; influenza virus, 1), viral culture of throat swabs (enterovirus, 8 cases; and adenovirus, 1), high-level antinuclear antibodies (>1/400, 3 cases), and thyroid-stimulating hormone (15 abnormal results). Antibodies to Toxoplasma and cytomegalovirus, enterovirus recovered from rectal swabs, and low-level antinuclear antibodies were seen with equal frequency in patients and controls. Using our evaluation strategy, the number of pericardial effusions classified as idiopathic was less than in other series. Systematic testing for Q fever, Mycoplasma pneumoniae, thyroid abnormalities, and antinuclear antibodies, accompanied by viral throat cultures, frequently enabled us to diagnose diseases not initially suspected in patients with pericardial effusion.

Can simple Doppler measurements estimate interatrial conduction time?

UNLABELLED: Prolongation of the interatrial conduction time (ia-CT) is considered an important factor in the pathophysiology of atrial fibrillation (AF) and as a criterion to perform multisite atrial pacing. Measurement of ia-CT requires an electrophysiologic study. The aim of this study was to compare echocardiographic with electrophysiologic measurements to determine if they are correlated. METHODS AND RESULTS: The study included 32 consecutive patients who underwent electrophysiologic studies. We measured ia-CT between the high right atrium and the distal coronary sinus. In all patients we measured P wave duration, left atrial diameter and area, and ia-CT by Doppler echocardiography was measured as the difference in time intervals between the QRS onset and the tricuspid A wave, and the QRS onset and the mitral A wave (DT). Ia-CT was statistically correlated with DT (r = 0.79, P < 0.0001), but not with P wave duration or left atrial dimensions. CONCLUSIONS: Measurement DT may be reliable to estimate ia-CT without invasive procedure. Accordingly, DT could be used as a simple selection criterion when considering patients for atrial resynchronization therapy.