Validation and clinical use of a novel diagnostic device for screening of atrial fibrillation.

AIMS: Patients with asymptomatic and undiagnosed atrial fibrillation (AF) are at increased risk of heart failure and ischaemic stroke. In this study, we validated a new diagnostic device, the MyDiagnostick, for detection of AF by general practitioners and patients. It records and stores a Lead I electrocardiogram (ECG) which is automatically analysed for the presence of AF. METHODS AND RESULTS: In total, 192 patients (age 69.4 ± 12.6 years) were asked to hold the MyDiagnostick for 1 min, immediately before a routine 12-lead ECG was recorded. Atrial fibrillation detection and ECGs stored by the MyDiagnostick were compared with the cardiac rhythm on the 12-lead ECG. In a second part of the study, the MyDiagnostick was used to screen for AF during influenza vaccination in the general practitioner's office. Atrial fibrillation was present in 53 out of the 192 patients (27.6%). All AF patients were correctly detected by the MyDiagnostick (sensitivity 100%; 95% confidence interval 93-100%). MyDiagnostick AF classification in 6 out of 139 patients in sinus rhythm was considered false positive (specificity 95.9%; 95% confidence interval 91.3-98.1%). During 4 h of influenza vaccination in 676 patients (age 74 ± 7.1 years), the MyDiagnostick correctly diagnosed AF in all 55 patients (prevalence 8.1%). In 11 patients (1.6%), AF was not diagnosed before, all with a CHA2DS2VASc score of >1. CONCLUSION: The high AF detection performance of the MyDiagnostick, combined with the ease of use of the device, enables large screening programmes for detection of undiagnosed AF.

Assessment of quantitative hypertrophy scores in hypertrophic cardiomyopathy: magnetic resonance imaging versus echocardiography.

To compare the diagnostic value of spin-echo magnetic resonance (MR) imaging and transthoracic echocardiography in quantitative assessment of the extent of hypertrophy in patients with hypertrophic cardiomyopathy (HCM), we examined 52 consecutive patients with HCM. The Spirito-Maron and Wigle hypertrophy scores were calculated with wall thickness measurements obtained by both imaging modalities. MR imaging yielded complete assessment of anatomic features and allowed calculation of hypertrophy scores in 49 patients (94%). Adequate echocardiograms were obtained in 33 patients (63%) and correlated well with MR imaging for wall thickness measurements and for determination of the two hypertrophy scores (both r> 0.9). MR imaging provided additional information not available by echocardiography in 16 patients (31%). We conclude that the Spirito-Maron and Wigle hypertrophy scores correlated well between echocardiography and MR imaging. Because echocardiography was of insufficient quality for calculating adequate hypertrophy scores in 19 (37%) patients, MR imaging provided the most comprehensive diagnostic information in patients with HCM.

New diagnostic options in hypertrophic cardiomyopathy.

The pathophysiologic features and clinical manifestations of HCM have been elucidated by the introduction of several new diagnostic options. Knowledge of the molecular defects of HCM has advanced rapidly, and genetic screening studies have reemphasized the value of the standard electrocardiogram as an initial screening tool. Analysis of heart rate variability, late potentials, and QT dispersion were not found to be reliable prognostic markers in HCM. However, measurement of dispersion of conduction is probably a sensitive technique in identifying a high risk for sudden cardiac death. Significant developments include transthoracic and transesophageal echocardiography and their role in studying the mitral valve, early detection of left ventricular chamber dilatation, analysis of coronary flow, and intraoperative echocardiography. Finally, advances in the application of magnetic resonance imaging and positron-emission tomography are underway.

Effects of permanent dual chamber pacing on myocardial perfusion in symptomatic hypertrophic cardiomyopathy.

OBJECTIVE: Angina and the presence of myocardial ischaemia are common in hypertrophic cardiomyopathy. Dual chamber pacing results in clinical improvement in these patients. This study evaluates the effects of permanent dual chamber pacing on absolute regional myocardial perfusion and perfusion reserve. SETTING: University hospital. PATIENTS AND DESIGN: Six patients with hypertrophic cardiomyopathy and severe symptoms of angina received a dual chamber pacemaker. Absolute myocardial regional perfusion and perfusion reserve (dipyridamole 0.56 mg/kg) were measured by dynamic positron emission tomography with 13N-ammonia both during sinus rhythm and 3 months after pacemaker insertion. Results were compared with those from 28 healthy volunteers. RESULTS: Pacing resulted in a reduction of anginal complaints and a reduction in intraventricular pressure gradient from 65 (SD 30) mm Hg to 19 (10) mm Hg. During sinus rhythm, baseline perfusion was higher in patients with hypertrophic cardiomyopathy than controls (184 (31) v 106 (26) ml/min/100 g, P < 0.01), and perfusion reserve was lower (1.6 (0.4) v 2.8 (1.0), P < 0.05). During pacing myocardial perfusion decreased to 130 (27) ml/min/100 g (P < 0.05), with variable responses in terms of perfusion reserve. Pacing caused a redistribution of myocardial stress perfusion and perfusion reserve. The coefficient of regional variation of myocardial stress perfusion decreased from 19.7 (7.0)% to 14.6 (3.9)% during pacing (12.9 (3.8)% in controls, P < 0.01). The coefficient of regional variation of perfusion reserve decreased from 16.7 (6.6)% to 11.4 (2.6)% during pacing (9.8 (4.1)% in controls, P < 0.01). CONCLUSIONS: Pacing caused a decrease of resting left ventricular myocardial blood flow and blood flow during pharmacologically induced coronary vasodilatation. Although global perfusion reserve remained unchanged, myocardial perfusion reserve became more homogeneously distributed.

Redistribution of myocardial perfusion during permanent dual chamber pacing in symptomatic non-obstructive hypertrophic cardiomyopathy: a quantitative positron emission tomography study.

Dual chamber pacing causes significant symptomatic improvement in many patients with hypertrophic cardiomyopathy. The mechanism behind this beneficial response is not fully understood. Positron emission tomography showed a redistribution of myocardial flow during pacing in a patient with non-obstructive hypertrophic cardiomyopathy. Early septal activation reduced septal fibre strain and blood flow and increased septal perfusion reserve.

Favourable outcome in idiopathic ventricular fibrillation with treatment aimed at prevention of high sympathetic tone and suppression of inducible arrhythmias.

OBJECTIVE: In the absence of an obvious cause for cardiac arrest, patients with idiopathic ventricular fibrillation are difficult to manage. A subset of patients has inducible arrhythmias. In others sympathetic excitation plays a role in the onset of the cardiac arrest. This study evaluates a prospective stepped care approach in the management of idiopathic ventricular fibrillation, with therapy first directed at induced arrhythmias and secondly at adrenergic trigger events. SETTING: University Hospital. PATIENTS: 10 consecutive patients successfully resuscitated from idiopathic ventricular fibrillation. INTERVENTIONS: Programmed electrical stimulation to determine inducibility, followed by serial drug treatment. Assessment of pre-arrest physical activity and mental stress status by interview, followed by beta blockade. Cardioverter-defibrillator implantation in non-inducible patients not showing significant arrest related sympathetic excitation. MAIN OUTCOME MEASURE: Recurrent cardiac arrest or ventricular tachycardia. RESULTS: Five patients were managed with serial drug treatment and four with beta blockade. In one patient a defibrillator was implanted. During a median follow up of 2.8 years (range 6 to 112 months) no patient died or experienced defibrillator shocks. One patient had a recurrence of a well tolerated ventricular tachycardia on disopyramide. CONCLUSIONS: Idiopathic ventricular fibrillation may be related to enhanced sympathetic activation. Prognosis may be favourable irrespective of the method of treatment. Whether the present approach enhances prognosis of idiopathic ventricular fibrillation remains to be determined. However, it may help to avoid potentially hazardous antiarrhythmic drugs or obviate the need for implantation of cardioverter-defibrillators.

Acute intravenous versus chronic oral drug effects of verapamil on left ventricular diastolic function in patients with hypertrophic cardiomyopathy.

The effects of acute intravenous (i.v.) versus long-term oral (p.o.) verapamil administration on diastolic function were studied in 20 patients with hypertrophic cardiomyopathy (HCM). We used a tip manometer catheter to record left ventricular pressure (LVP) tracings and a nuclear probe to measure LV volume changes. Infusion of verapamil resulted in an increase in time constant of relaxation (+15%, p < 0.001); LV peak filling rate, heart rate (HR), and stiffness constant of the diastolic pressure-volume relation were unchanged. During 18-week p.o. verapamil treatment, HR decreased (-16%, p < 0.0005) and the atrial contribution to LV filling decreased (-27%, p < 0.05); other parameters differed significantly from baseline values. Results demonstrate that acute i.v. versus long-term p.o. verapamil administration have different effects on diastolic function in HCM.

Time course of hemodynamic changes and improvement of exercise tolerance after cardioversion of chronic atrial fibrillation unassociated with cardiac valve disease.

This study prospectively assessed the time course, magnitude and mechanism of the hemodynamic changes after restoration of sinus rhythm in patients with chronic atrial fibrillation (AF) unassociated with valvular disease. Severe cardiac dysfunction may occur after chronic supraventricular tachycardia in patients with and without underlying cardiac disease. Improvement may follow abolishment of the arrhythmia or adequate slowing of the ventricular rate. Eight patients were studied with a mean previous duration of AF of 10 +/- 9 months. Ejection fraction, exercise capacity and the atrial contribution to the left ventricular filling (only during sinus rhythm) were studied before cardioversion, after cardioversion and 1 week, 1 month and 6 months thereafter. A significant improvement in ejection fraction from 36 +/- 13 to 53 +/- 8% (p < 0.05) occurred at 1 month after cardioversion. Concomitantly, peak oxygen consumption had increased at 1 month, from 20.1 +/- 7 to 25.2 +/- 6 ml/min/kg (p < 0.05). Thereafter, no further improvement in hemodynamic parameters occurred. The atrial systole improved already at 1 week (from 3 +/- 5 to 16 +/- 11%, p < 0.05) and remained unchanged thereafter. Thus, restoration of sinus rhythm was associated with a delayed improvement in ejection fraction and maximal exercise capacity, preceded by an early restoration of atrial contractility and an acute slowing of the heart rate. The discrepancy in time course of restoration of atrial and ventricular function parameters suggests that an intrinsic left ventricular cardiomyopathy is present in patients with AF.

Sustained-release diltiazem versus metoprolol in stable angina pectoris.

The efficacy of sustained-release diltiazem (diltiazem-SR) 120 mg b.i.d. was compared with metoprolol 100 mg b.i.d. in 12 patients with stable angina. Following a 1-week placebo period, patients received diltiazem-SR or metoprolol in two 3-week treatment periods, in a randomized double-blind crossover design. Total exercise time was increased more with diltiazem-SR than with metoprolol (1.2 min vs 0.4 min, P = 0.02), although the reduction in frequency of weekly anginal attacks was equal with both drugs (5 +/- 3 with placebo to 1 +/- 1 with both drugs). The difference between diltiazem-SR and metoprolol may, in part, be due to the fact that the tests were performed 12 h after drug administration. The diltiazem plasma levels were in the therapeutic range; metoprolol plasma levels, in contrast, were all below the therapeutic range. In addition, the patients might be tired out earlier during beta-blockade therapy, because a greater increase in exercise time with diltiazem-SR compared with metoprolol was found in those patients in whom the exercise endpoint changed from angina to fatigue. Thus, diltiazem-SR effectively reduces the frequency of anginal attacks when given twice daily, and improves exercise capacity to a greater extent than metoprolol 12 h after last dose.