L. De Ambroggi

Mapping of body surface potentials in patients with the idiopathic long QT syndrome.

Body surface potential maps were recorded from 140 chest leads in 25 patients affected by the idiopathic long QT syndrome (LQTS) and in 25 healthy control subjects matched for age and sex. Potential time integrals of the QRST and ST-T intervals were calculated at each lead point and displayed as isointegral (ISOI) maps. The main abnormalities noted on the QRST and ST-T ISOI maps were one area of negative values larger than normal in the right anterior and inferior thorax and a complex multipeak distribution of the integral values. At least one abnormality was present in 19 (76%) of the patients with LQTS and four (16%) of the control subjects (p less than .001). Each ISOI map was also represented as a weighted sum of nine fundamental components (eigenvectors) to detect and quantitate the nondipolar content. The percent contribution of the nondipolar eigenvectors (all eigenvectors beyond the third) was significantly higher in the LQTS group than in the control group (p less than .005). Specifically, an abnormally high nondipolar content on the QRST ISOI maps was observed much more frequently for patients with LQTS than for control subjects (nine or 36% vs one or 4%), and this was also true on the ST-T ISOI maps (14 or 56% vs one or 4%). No correlation was found between the major abnormalities on body surface maps and syncopal episodes. However, the high prevalence (76%) of these alterations among the patients with LQTS and their infrequent occurrence in the control population strongly suggests that they may be useful markers for the diagnosis of atypical cases. The prominent electronegative area on the anterior thorax can be related to delayed repolarization of a portion of the anterior wall of the heart. This finding is in agreement with the hypothesis that lower than normal right cardiac sympathetic activity is the main pathogenetic mechanism of LQTS. Multipeak distribution and high nondipolar content suggest regional electrical disparities in the ventricular recovery process. This may in part account for the high susceptibility of patients with LQTS to malignant arrhythmias.

Body-surface maps of heart potentials: tentative localization of pre-excited areas in forty-two Wolff-Parkinson-White patients.

SUMMARY Heart potentials were recorded from the entire chest surface in 42 patients suffering from Wolff-Parkinson-White syndrome. We were able to identify six types of surface maps, according to the location of the potential maximum and minimum during the delta wave. For each of these types we suggested the most likely location of the pre-excited region around the A-V rings (types 1 to 5) or in the interventricular septum (type 6). In 13 patients belonging to Types 1, 2, 3, 5 and 6 our hypotheses were in agreement with intracardiac recordings, epicardial maps or surgical results obtained by others. Isopotential surface maps provide more information on the location of the pre-excited area than conventional ECGs, particularly when these exhibit intermediate features between Types A and B.

Proximal myotonic myopathy: a syndrome with a favourable prognosis?

Cardiac involvement in myotonic dystrophy type 1 (DM1) is well known. In contrast, the severity and frequency of cardiac abnormalities in proximal myotonic myopathy (PROMM) are still unclear. To identify similarities and differences in the rate of progression of muscle weakness and cardiac disturbances in these two disorders, 16 patients with PROMM (3q-unlinked PROMM: n=10; uniformative for linkage: n=6) were compared to 33 patients with moderately severe myotonic dystrophy type 1 (DM1). There was no significant difference in disease duration between PROMM and DM1. Patients underwent serial manual muscle strength testing, EKG, 24-h Holter monitoring, 2D-echocardiography. Muscle weakness progressed slowly in both groups. Most DM1 patients developed conduction defects. No significant atrioventricular disturbances on initial and follow-up examinations were found in PROMM patients. One patient developed right bundle branch block. Many families with PROMM appear to have more benign cardiac manifestations and less severe prognosis compared to DM1. Further studies of subgroups of PROMM (linked to the 3q21 locus and without linkage) are necessary to determine whether the cardiac conduction disturbances are more common in a specific genotype of PROMM.

Surgical treatment of ventricular septal defect complicating acute myocardial infarction. Experience of a north Italian referral hospital

The purpose of our study was to evaluate the clinical outcome of postinfarction ventricular septal defect (VSD) of patients referred to our institution for surgical treatment, by assessing the role of several operative, pre- and post-operative variables on mortality. The medical records of 58 consecutive patients (mean age 73+/-7 years), operated on after 14+/-12 days from the acute myocardial infarction were retrospectively reviewed and the data were analyzed. Associated procedures were left ventricular reconstruction in 13 patients and aortocoronary bypass grafting in 47 (81%). The overall operative, in-hospital mortality rate was 52% (75% in patients operated on within the first week and 16% if time from infarct to surgery was >3 weeks). Time from AMI to surgery and time from hospital admission to operation were significantly shorter in non-survivors (p=0.003 and 0.012, respectively). Other pre-operative variables significantly associated with mortality were: cardiogenic shock, pulmonary pressure, VSD diameter. In conclusion, time from AMI to operation appears to be a very important prognostic factor. However, size of VSD and hemodynamic conditions significantly influence the mortality. Moreover, concomitant procedures of revascularization can be safely performed, when required, as actually occurs in most cases.

The frequency and severity of cardiac involvement in myotonic dystrophy type 2 (DM2): Long-term outcomes

BACKGROUND Frequency and severity of cardiac involvement in DM2 are still controversial. The aims of our study were to determine the frequency and progression of cardiac and muscle involvement in a relatively large cohort of patients with DM2 throughout Italy and Germany and to provide long-term outcomes in this disorder. METHODS 104 DM2 and 117 DM1 patients underwent baseline and follow-up assessments of, ECG, 24h Holter monitoring, 2D echocardiography and electrophysiological study (EPS) when appropriate, and manual muscle strength testing (mean follow-up: 7.4 ± 4.1 for DM2 and 5.7 ± 4 years for DM1). RESULTS Overall, 10% of DM2 patients vs 31% of DM1 patients had PR ≥ 200 ms and 17% of DM2 patients vs 48% of DM1 patients had QRSD ≥ 100 ms. Six patients with DM2 vs 28 patients with DM1 required PM/ICD implantations. DM2 patients were stronger than DM1 patients at baseline, but muscle strength worsened significantly over time (p<0.0001), just as in DM1, although at a slower annual rate. CONCLUSION Our data demonstrate that the frequency and severity of cardiac involvement and of muscle weakness are reduced in DM2 compared to DM1 and that progression is slower and less severe. Nonetheless, careful cardiac evaluation is recommended in this patient population to identify patients at risk for potential major cardiac arrhythmias.

Gender differences in stability of the instantaneous patterns of body surface potentials during ventricular repolarisation

Women have a higher risk of developing torsade de pointes under QT-prolonging conditions. The electrophysiological differences between the sexes that could account for this are largely unknown. The objective of the work was to evaluate gender differences in repolarisation potentials using a method that is independent of the specific electrical properties of the thorax. 1410 normal recordings from the Glasgow 12-lead ECG database and 52 normal ECG maps obtained separately in Milan were analysed. The average difference between 1 and the correlation coefficient of the instantaneous pattern at the peak of T with that at every other instant is called the early repolarisation deviation index (ERDI) for J-T peak and the late repolarisation deviation index (LRDI) for T peak-T end. In standard ECG recordings, the ERDI was 0.42±0.22 in females compared with 0.19±0.16 in males (p<10−6). The LRDI was higher in males under the age of 50. In body surface maps, the ERDI was 0.32±0.21 in females against 0.16±0.17 in males (p<0.01), and the LRDI was non-significantly higher in males. The pattern of instantaneous body surface potentials showed gender differences during repolarisation with a method that is independent of the electrical properties of the thorax.

Drug Abuse in Cardiovascular Diseases

A large amount of substances and their association can lead to worsening of latent or active cardiovascular diseases and, sometimes, to ex-novo cardiovascular diseases.

Effect of nitroglycerin on ST potentials in the post-acute phase of myocardial infarction

Thoracic electromaps were recorded before and after sublingual nitroglycerin (NG) in 26 subjects 15 and 30 days after acute myocardial infarction (MI), in order to evaluate the effect of the drug on injury potentials. Ten patients with documented left ventricular aneurysm were also studied 5 to 46 months after acute MI. Fifteen min after NG there was a significant decrease, compared with basal values, of ST segment elevations, blood pressure and rate-pressure product on both the 15th and 30th days. The degree of ST potentials reduction was not strictly related to the decrease of myocardial oxygen consumption, as indicated by the rate-pressure product. The response to NG on the 15th day did not predict accurately the evolution of injury potentials. In fact there was no significant correlation between percentages reduction of ST after NG on the 15th day and amplitudes of ST segment elevations present on the 30th day. In the patients with ventricular aneurysm, ST potential decrease and hemodynamic changes after NG were similar to those observed in the other groups studied. Our data suggest that it is not possible to differentiate between ST segment elevations associated with a dyssynergic area and those merely due to ischemic injury on the basis of NG sensitivity, and that ST segment elevations in the acute and subacute phase and long after MI have, at least in part, a similar electrophysiological significance.