Friday, March 31, 2017

Torsades de pointes - twisting of the points

Torsades de pointes is a polymorphic ventricular tachycardia that occurs frequently in cases of QT interval prolongation.

This can be due to congenital or acquired Long QT interval syndrome.

It is characterized by a progressive change of the electrical axis, typically rotating 180 degrees in approximately 10 to 12 cycles and the amplitude, as though the depolarization and repolarization of the ventricle was turning on a point.

This results in the characteristic sinusoidal twisting of the peaks of the QRS complexes around the isoelectric line of the recording.


The tachycardia rate typically is in the range of 150 to 300 beats/min.

It is usually a self-limiting arrhythmia that spontaneously dies out after a few tens of cycles and only in a minority of cases that it degenerates into ventricular fibrillation and can lead to sudden cardiac death.

Drugs that can prolong the QT interval and induce Torsades de pointes are:

It can also be caused by electrolyte imbalances like, hypokalemia, hypomagnesemia and less commonly hypocalcemia.

First published on: 31 March 2017

Tuesday, December 27, 2016

Endomysium, Perimysium and epimysium - definition, histology

Each muscle fibre is closely surrounded by connective tissue.
This acts as a support for the muscle fibres and unites them to each other.

1) Each muscle fibres is surrounded by delicate connective tissue that is called the endomysium.
2) Individual fasciculi are enclosed by a stronger sheath of connective tissue called the perimysium.
3) The entire muscle is surrounded by connective tissue called the epimysium.

This is illustrated by the schematic diagram below.

1= perimysium, 2= endomysium, 3= fasciculus.

At the junction of a muscle with a tendon, the fibres of the endomysium, the perimysium and the epimysium become continuous with the fibres of the tendon.

First published on: 27 December 2016