The “Missing” Link Between Acute Hemodynamic Effect and Clinical Response

The hemodynamic, mechanical and electrical effects of cardiac resynchronization therapy (CRT) occur immediate and are lasting as long as CRT is delivered. Therefore, it is reasonable to assume that acute hemodynamic effects should predict long-term outcome. However, in the literature there is more evidence against than in favour of this idea. This raises the question of what factor(s) do relate to the benefit of CRT. There is increasing evidence that dyssynchrony, presumably through the resultant abnormal local mechanical behaviour, induces extensive remodelling, comprising structure, as well as electrophysiological and contractile processes. Resynchronization has been shown to reverse these processes, even in cases of limited hemodynamic improvement. These data may indicate the need for a paradigm shift in order to achieve maximal long-term CRT response

Animal Models of Dyssynchrony

Cardiac resynchronization therapy (CRT) is an important therapy for patients with heart failure and conduction pathology, but the benefits are heterogeneous between patients and approximately a third of patients do not show signs of clinical or echocardiographic response. This calls for a better understanding of the underlying conduction disease and resynchronization. In this review, we discuss to what extent established and novel animal models can help to better understand the pathophysiology of dyssynchrony and the benefits of CRT

Use of a radioactive tracer to study the nesting system of mastotermes darwiniensis froggat.

A new method for the tracing of termite nesting systems is proposed and proved in field trials with Mastotermes darwiniensis nesting systems. An attractive bait containing y-ray emitting scandium-46 oxide is inserted into an infested site. The bait is eaten rapidly and taken to the nests where trophallactic transfer spreads the scandium through the colony members. The scandium is finally excreted and the excreta fixed in the gallery walls and carton of all sub-centres which can then be found using a y-ray detector. The use of other radionuclides as colloids in similar bait is described. This new method appears to introduce a new concept into the tracing of social insects

Left ventricular endocardial pacing in cardiac resynchronisation therapy: Moving from bench to bedside

In cardiac resynchronisation therapy, failure to implant a left ventricular lead in a coronary sinus branch has been reported in up to 10% of cases. Although surgical insertion of epicardial leads is considered the standard alternative, this is not without morbidity and technical limitations. Endocardial left ventricular pacing can be an alternative as it has been associated with a favourable acute haemodynamic response compared with epicardial pacing in both animal and human studies. In this paper, we discuss left ventricular endocardial pacing and compare it with epicardial surgical implantation. Ease of application and procedural complications and morbidity compare favourably with epicardial surgical techniques. However, with limited experience, the most important concern is the still unknown long-term risk of thromboembolic complications. Therefore, for now endovascular implants should remain reserved for severely symptomatic heart failure patients and patients at high surgical risk of failed coronary sinus implantation