Just this morning I noticed a book by G. Ottaviani Springer called "Crib Death - Sudden Unexplained Death of Infants, a Pathologists View"
I checked it out and it had part of the appendix dedicated to Long QT Syndrome. This is a very recent book. I don't claim to know anything about this subject, so I thought I'd post the section for you in case it was something that you can use.
"IV.2.7 Long QT Syndrome
A notable example of multifocal apoptotic degeneration of the sinus node occurs in
victims dying of the LQT syndrome, a clinical entity characterized by sinus bradycardia
[96, 105, 210]. Sudden unexpected death is one of the clinical characteristics
of the LQT syndrome and has often been found to be mediated by lethal ventricular
arrhythmias. It is logical to anticipate that the normal occurrence of apoptotic cell
death during postnatal morphogenesis of the sinus node will periodically distort
or suppress normal sinus rhythm [106]. Moreover, in the LQT syndrome apoptotic
destruction involves not only the myocytes of the sinus node but also many local
nerves and ganglia [96, 105].
QT prolongation could be dangerous in babies and a possible cause of their fatal
arrhythmia [76, 260], but solid evidence of its occurrence is still lacking and such an
association is still a matter of controversy. The capricious nature of episodic QT prolongation
documented in human infants poses difficulties in demonstrating lethal
cardiac electrical instability [96, 210].
Schwartz et al. [254], in a 19-year prospective study, performed follow-up electrocardiography
in an unselected population of over 33,000 infants, and concluded
that congenital prolongation of the QT interval accounts for a proportion of SIDS
cases. Their results underline the potential value of neonatal electrocardiographic
screening for an early identification of a prolonged long QT interval and consequent
preventive treatment of the affected infants [221, 254]. However, Schwartz
et al. admitted that the LQT syndrome may account for only a fraction of the crib
death cases, and precise quantification of this fraction remains difficult despite the
data obtained from their large epidemiological study [254, 255]. Guntheroth and
Spiers [76] state that submitting all infants and newborns to electrocardiographic
screening would be ineffective and a waste of medical resources, and it would cruelly
alarm thousands of parents.
Recent studies also indicate further close clinicopathogenetic analogies with arrhythmogenic
lethal late repolarization, attended by fetal developmental impairments
of the conduction system, often resulting in accessory AV pathways, whose
high frequency in SIDS has been documented in the present cases and is entirely
consistent with junctional tachycardia [247]. An important report, in this connection,
is that of Kuo et al. [126] who emphasize the possible role of the conduction system
among the ontogenetic substrates of the Ito abnormalities. This genetic clinicopathological
suggestion is further substantiated by recent work coauthored by Rossi
[16] on the life-threatening potential of WPW syndrome, whose common accessory
AV pathway substrate was proven occasionally to have a genetic association [67].
Viskin et al. [276] recommend genetic screening in every case of probable LQT
syndrome, and state that a positive result will confirm the diagnosis but that no
mutations are found in many patients with a definite diagnosis of LQT syndrome, so
a negative result is not very helpful. In any case, genetic testing might take months,
and the patient needs treatment [210, 276]."
