Optical mapping of ventricular arrhythmias in LQTS mice with SCN5A mutation N1325S

Transgenic expression of SCN5A mutation N1325S creates a mouse model for type-3 long QT syndrome (LQT3), TG-NS/LQT3. Optical mapping is a high temporal and spatial resolution fluorescence mapping system that records 256 action potentials simultaneously in a Langendorff-perfused heart. Here for the first-time, we provide a spatial view of VT in a genetic LQT3 model using optical mapping. Spontaneous VT was detected in TG-NS/LQT3 hearts, but not in littermate control hearts. VT was initiated primarily by activation of a new firing focus as well as functional conduction block of new activation waves. New firing was initiated at many different Loci in the heart, suggesting that "increased automaticity" is a key mechanism for initiation of VT. The sustained VT was maintained by a reentry mechanism. Nifedipine, an L-type calcium channel blocker, decreased the frequency of VT, indicating the involvement of abnormalities of the calcium homeostasis in the genesis of VT in TG-NS/LQT3 mice.

Cardiac involvement and CTG expansion in myotonic dystrophy

Although cardiac complications are well known in myotonic dystrophy (DM), patients rarely manifest symptoms of cardiac disease, and if so they most often show conduction abnormalities or arrhythmia. In this study, specific cardiac findings were reviewed in 79 patients with DM. No correlation was found between the cardiac assessments and the CTG expansion. Thus, for a single patient the cardiac involvement in the disease can not be predicted from the findings of the genetic investigation. On the other hand, a clear positive relationship of the PR interval with the QRS duration was revealed, as well as a positive correlation between the age of the DM patient and the QRS duration, which increases with 0,54 ms/year. Systolic dysfunction, evaluated by transthoracic echocardiography, seems to be quite uncommon. In 32 % of the patients with a normal ECG, the 24 h Holter monitoring showed arrhythmias and conduction abnormalities. Based on these findings we recommend a follow up of DM patients not only based on the ECG, but also through 24 h Holter monitoring.

Influence of transgenic overexpression of phospholamban on postextrasystolic potentiation

Twelve mice with PLB overexpression (PLBOE), and 11 isogenic FVB/N wild-type (WT) controls, were anesthetized and instrumented with a 1.4 F Millar catheter in the LV and a 1 F pacemaker in the right atrium. At a cycle length of 200 ms and a fixed extrastimulus of 120 ms, extrastimuli with increasing intervals (PESI) up to 1000 ms were introduced, and the peak rates of LV isovolumic contraction (+/- dP/dtmax) were normalized and fit to monoexponential equations. In a subset of animals, the protocols were repeated after ryanodine (4 ng/g) was given to deplete SR Ca2+ stores. The time constant and the plateau of the exponential curve fits were significantly greater in PLBOE than WT (107.8 +/- 7.0 v 75.2 +/- 5.5 ms and 1.39 +/- 0.03 v 1.08 +/- 0.02, both P < 0.05). At 200, 600 and 1000 ms, the normalized dP/dt was significantly greater in PLBOE than WT. After ryanodine, normalized dP/dt was significantly decreased in PLBOE, but unchanged in WT. The protein levels of the sodium-calcium exchanger normalized to calsequestrin were increased 3.7 +/- 0.3-fold in PLBOE compared to controls. In conclusion, the phospholamban level is a critical determinant of postextrasystolic potentiation in this transgenic model, and is differentially impaired by ryanodine at long diastolic intervals in PLBOE v controls. These differences may be due in part to changes in the protein level and resultant activity of the sodium calcium exchanger.

[Familial polymorph ventricular extrasystole associated with Pierre Robin syndrome]

In a family of 9 persons over 3 generations, 6 had incessant polymorphic ventricular extrasystoles, often in salves, resembling unsustained bidirectional ventricular tachycardia. Ventricular repolarisation was abnormal with giant U waves. Five persons had suffered syncopes. All had a facial abnormality: one woman had a complete Pierre Robin syndrome with mandibular hypoplasia, glossoptos and cleft palate; in the other cases, minor forms were observed, with micrognathia and ogival palate. Two patients had bone abnormalities of the feet with total agenesis of the last 2 phalanges of several toes. This familial polymorphic ventricular extrasystole with repolarisation abnormalities has many features in common with the congenital long QT syndrome; associated with the Pierre Robin syndrome and bone abnormalities of the extremities it would seem to be a new multiple congenital abnormalities syndrome.

Ventricular extrasystoles with syncopal episodes, perodactyly, and Robin in sequence in three generations: a new inherited MCA syndrome?

We observed the combination of the Robin sequence with perodactyly (hypoplasia and/or agenesis of the distal phalanx of the toes) and cardiac arrhythmia (ventricular extrasystoles occurring as bigemini or multifocal tachycardia with syncopal episodes) in 6 relatives in 3 generations. This familial association has not been reported before and probably represents a previously unrecognized heritable malformation syndrome.

[Familial manifestation of idiopathic atrial flutter]

We describe, to the best of our knowledge for the first time, the occurrence of idiopathic atrial flutter (AF) in two male children of a family. The two brothers are the third and sixth of seven children, and the only males. The parents do not suffer from any heart disease. The first sister died in Turkey at the age of twenty days. The parents do not know the cause of death. The fourth sister died at de age of five years, also in Turkey, probably because of meningitis. Electrocardiograms of the parents and the other three sisters are normal. Besides the unique familial occurrence, the AF themselves offer some unusual features. In the first patient, the AF could not be converted to sinus rhythm. In the second patient, the AF occurred paroxysmally, and in addition to the AF, the electrocardiogram tracings revealed paroxysmal atrial tachycardia.

Familial bidirectional ventricular tachycardia

The occurrence of incessant ventricular arrhythmia with bouts of polymorphous and bidirectional ventricular tachycardia is described in two totally asymptomatic sisters, with structurally normal hearts and no QT prolongation. Familial survey revealed the occurrence of increased ventricular ectopic activity in the father, brother and another sister.

Successful control of refractory ventricular premature beat with an estrogen-progesterone compound

Drug resistant ventricular premature contractions (VPCs) in a 35-yr-old woman were successfully controlled with a contraceptive agent containing estrogen-progesterone. The VPCs in this patient always showed an R on T phenomenon resulting in occasional short run of ventricular tachycardia. Apart from the VPCs, her ECG exhibited no abnormalities. The family history revealed 9 instances of sudden unexpected death over 3 generations. The findings of myocardial biopsy of the right ventricular endocardium were characteristic of cardiomyopathy. This report discusses the possibility that a contraceptive agent successfully suppressed VPCs in a particular woman who showed a close relation between a certain period of her menstrual cycle and the occurrence of VPCs.