Several medicines, including cancer therapies, are known to alter the electrophysiological function of ventricular myocytes resulting in abnormal prolongation and dispersion of ventricular ...repolarization (quantified by multi-lead QTc measurement). This effect could be amplified by other concomitant factors (e.g., combination with other drugs affecting the QT, and/or electrolyte abnormalities, such as especially hypokalemia, hypomagnesaemia, and hypocalcemia). Usually, this condition results in higher risk of torsade de point and other life-threatening arrhythmias, related to unrecognized unpaired cardiac ventricular repolarization reserve (VRR). Being VRR a dynamic phenomenon, QT prolongation might often not be identified during the 10-s standard 12-lead ECG recording at rest, leaving the patient at increased risk for life-threatening event. We report the case of a 49-year woman, undergoing tamoxifen therapy for breast cancer, which alteration of ventricular repolarization reserve, persisting also after correction of concomitant recurrent hypokalemia, was evidenced only after manual measurements of the corrected QT (QTc) interval from selected intervals of the 12-lead ECG Holter monitoring. This otherwise missed finding was fundamental to drive the discontinuation of tamoxifen, shifting to another “safer” therapeutic option, and to avoid the use of potentially arrhythmogenic antibiotics when treating a bilateral pneumonia in recent COVID-19.
ECG-documented AF recurrences were most frequent in Group 4 patients, with a significant correlation between BMI behavior and the time interval between subsequent recurrences (every 2.6 months Group ...4, 5.5 months Group 3, 13.7 months Group 2, and 15.2 months Group 1). ...we can confirm that BMI reduction has a preventive effect against AF recurrence and that the LEGACY study results can be applied also to Mediterranean patients.
Background: To determine the prevalence of anti-β-adrenoceptors autoantibodies (aβAA) in patients with idiopathic arrhythmias (IA) and to assess whether aβAA are predictive markers for concealed ...cardiomyopathy in such patients. Methods and Results: Sixty-seven patients (group 1) with IA 25 supraventricular (SVA) and 42 ventricular (VA); 14 patients (group 2) with suspected cardiomyopathy, 12 patients with definite cardiomyopathy (group 3); and 19 healthy controls (group 4) were tested with an enzyme immunoassay, using synthetic peptides corresponding to the second extracellular loop of the human β1-and β2-adrenoceptors. Endomyocardial biopsy was performed in 29 patients. As compared with group 4 3/19 (15.7%), anti-β1-adrenoceptor autoantibodies (aβ1AA) were more frequent in group-1 patients 38/67 (56.7%; P<0.01): 27/42 (64.2%; P<0.001) with VA and 11/25 (44%; P<0.05) with SVA. 3 of the group 1 patients also had anti-β2-adrenoceptor autoantibodies (aβ2AA). 4 were positive for aβ2AA only. Biopsy performed in 11/67 group 1 patients was abnormal in all. Of them, 7/8 (87.5%) with VA and 3/3 (100%) with SVA were positive for aβ1AA. PCR analysis from paraffin blocks of the 11 group 1 biopsied patients was negative for EV, EBV, HCV, AV, PVB19, INF A/B,HSV1/2, HHV6 and HHV8 viral genomes. Conclusions: The second extracellular loop of the β-adrenoceptor is the molecular target of specific autoantibodies. Positivity for aβ1AA predicts abnormal histological findings in 90% of IA patients and suggests that autoimmunity might play an arrhythmogenic role. (Circ J 2012; 76: 1345-1353)
Ventricular arrhythmias are frequently observed in the elderly population secondary to alterations of electrophysiological properties that occur with the normal aging process of the heart. However, ...the underlying mechanisms remain poorly understood. The aim of the present study was to determine specific age-related changes in electrophysiological properties and myocardial structure in the ventricles that can be related to a structural-functional arrhythmogenic substrate. Multiple unipolar electrograms were recorded in vivo on the anterior ventricular surface of four control and seven aged rats during normal sinus rhythm and ventricular pacing. Electrical data were related to morphometric and immunohistochemical parameters of the underlying ventricular myocardium. In aged hearts total ventricular activation time was significantly delayed (QRS duration: +69%), while ventricular conduction velocity did not change significantly compared with control hearts. Moreover, ventricular activation patterns displayed variable numbers of epicardial breakthrough points whose appearance could change with time. Morphological analysis in aged rats revealed that heart weight and myocyte transverse diameter increased significantly, scattered microfoci of interstitial fibrosis were mostly present in the ventricular subendocardium, and gap junction connexin expression decreased significantly in ventricular myocardium compared with control rats. Our results show that in aged hearts delayed total ventricular activation time and abnormal activation patterns are not due to delayed myocardial conduction and suggest the occurrence of impaired impulse propagation through the conduction system leading to uncoordinated myocardial excitation. Impaired interaction between the conduction system and ventricular myocardium might create a potential reentry substrate, contributing to a higher incidence of ventricular arrhythmias in the elderly population.
The reported case, a spin-off of a wider ongoing national study investigating the individual stress reactions of police officers during realistic police tactical training, highlights the eventuality ...that stress-induced paroxysmal arrhythmias might occur and remain undetected without ECG monitoring as a standard practice. The ECG of a 41-year-old frontline police officer (and professional athlete of the State Police’s rugby team) was monitored with a wireless, textile-based, wearable device during stressful scenarios implying the use of force. ECG data were processed with the Kubios software to assess training-induced time-varying changes of heart rate variability parameters and of the parasympathetic, sympathetic, and stress indices. Multiparametric analysis of the heart rate variability quantified remarkable stress-induced increment of vagal withdrawal and of sympathetic dominance, with exceptionally high-stress index and sudden occurrence of a wide-QRS paroxysmal tachyarrhythmia (240 bpm) with concomitant operational failure. Subsequent exhaustive mandatory clinical assessment excluded any structural and arrhythmogenic cardiac abnormality. Although exceptional and to the best of our knowledge so far unique, the recording of a stress-induced paroxysmal wide-QRS arrhythmia occurring during realistic tactical training in a healthy police officer and highly fit athlete is worth to be shared as a caveat about the potential risk if eventually occurring in officers with unknown cardiovascular risk factors (e.g., for ischemic heart disease). Moreover, the demonstration that such a high level of stress may occur even in an experienced, healthy, and highly fit officer altering the physiologic dynamicity of brain–heart interaction with a negative consequence on the operational outcome strongly suggests that individual emotional reactions induced by stressful duty events must be safely experienced and assessed with realistic training, to adopt preventive coping strategies, to improve police officers’ efficiency in front of threats, and to lower the risk of inappropriate use of force with dramatic consequences on the street.
Background
P‐wave duration, its dispersion and signal‐averaged ECG, are currently used markers of vulnerability to atrial fibrillation (AF). However, since tangential atrial currents are better ...detectable at the body surface as magnetic than electric signals, we investigated the accuracy of magnetocardiographic mapping (MCG), recorded in unshielded clinical environments, as predictor of AF occurrence.
Methods
MCG recordings, in sinus rhythm (SR), of 71 AF patients and 75 controls were retrospectively analyzed. Beside electric and magnetic P‐wave and PR interval duration, two MCG P‐wave subintervals, defined P‐dep and P‐rep, were measured, basing on the point of inversion of atrial magnetic field (MF). Eight parameters were calculated from inverse solution with “Effective Magnetic Dipole (EMD) model” and 5 from “MF Extrema” analysis. Discriminant analysis (DA) was used to assess MCG predictive accuracy to differentiate AF patients from controls.
Results
All but one (P‐rep) intervals were significantly longer in AF patients. At univariate analysis, three EMD parameters differed significantly: in AF patients, the dipole‐angle‐elevation angular speed was lower during P‐dep (p < 0.05) and higher during P‐rep (p < 0.001) intervals. The space‐trajectory during P‐rep and the angle‐dynamics during P‐dep were higher (p < 0.05), whereas ratio‐dynamics P‐dep was lower (p < 0.01), in AF. At DA, with a combination of MCG and clinical parameters, 81.5% accuracy in differentiating AF patients from controls was achieved. At Cox‐regression, the angle‐dynamics P‐dep was an independent predictor of AF recurrences (p = 0.037).
Conclusions
Quantitative analysis of atrial MF dynamics in SR and the solution of the inverse problem provide new sensitive markers of vulnerability to AF.
FENICI, R., et al.: Phantom Validation of Multichannel Magnetocardiography Source Localization.
Multichannel magnetocardiography (MMCG) is used clinically for noninvasive localization of the site of ...origin of cardiac arrhythmias. However, its accuracy in unshielded environments is still unknown. The aim of this study was to test the accuracy of three‐dimensional localization of intracardiac sources by means of MMCG in an unshielded catheterization laboratory using a saline‐filled phantom, together with a nonmagnetic catheter designed for multiple monophasic action potential recordings in a clinical setting. A nine‐channel direct current superconducting quantum interference device (DC‐SQUID) system (sensitivity fT/Hz0.5) was used for MMCG from 36 points in a measuring area of 20 × 20 cm. The artificial sources to be localized were dipoles embedded in the distal end of the catheter, placed 12 cm below the sensor's plane. Equivalent current dipoles, effective magnetic dipoles, and distributed currents models were used for the inverse solution. The localization error was estimated as the three‐dimensional difference between the physical position of the tip of the catheter and the three‐dimensional localization of the dipoles derived by means of the inverse solution calculated from MMCG data. The reproducibility was tested by repeating the MMCG after repositioning the phantom and the measurement system. The average location error of the catheter dipole was
9 ± 4 mm
and was due primarily to imprecise depth estimation. Localization was reproducible within 0.73 mm. The distributed currents model provided an accurate image of current distribution centered over the catheter tip. The authors conclude that MMCG estimation is accurate enough to guarantee proper localization of cardiac dipolar sources even in an unshielded clinical electrophysiological laboratory. (PACE 2003; 26Pt. II:426–430)
Magnetic field maps from (A) subjects without ischemia, showing a bipolar field map throughout the cardiac cycle, and (B) patients with acute coronary syndrome in whom a distorted, fragmented or ...multipolar field map characterizes active myocardial ischemia. Maps were recorded with a 15-channel magnetometry device and display the magnetic field distribution at the point of maximum rate of change between the Q and R peaks (QR) and between the R and S peaks (RS). Display omitted
The dipoles observed in subjects without ischemia are generally aligned in the same direction and have only a single positive (red) and single negative (blue) pole. The images from ischemic patients are generally more complex. A wider spread of angles and pole to pole distance, and the presence of more than two peaks are features that generally indicate ischemia.
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