Torsade de Pointes

Torsade de Pointes

http://www.emedicine.com/emerg/topic596.htm

1. Torsade de pointes (TDP), often referred to as torsade, is an uncommon variant of ventricular tachycardia (VT). The underlying etiology and management of torsade are, in general, quite different from those of garden-variety VT. The management of torsade with group IA antidysrhythmic drugs can have disastrous consequences. Differentiating between these entities, therefore, is critically important
2. Torsade is defined as a polymorphous VT in which the morphology of the QRS complexes varies from beat to beat
3. The ventricular rate can range from 150 beats per minute (bpm) to 250 bpm
4. There is regular variation of the morphology of the QRS vector from positive to net negative and back again. This was symbolically termed torsade de pointes, or "twisting of the point" about the isoelectric axis
5. definition also requires that the QT interval be increased markedly (usually to 600 msec or greater ). Cases of polymorphous VT, which are not associated with a prolonged QT interval, are treated as generic VT
6. The underlying basis for rhythm disturbance is delay in phase III of the action potential. The delay is mediated by the hERG potassium channel.
7. Women are 2-3 times more likely to develop TDP than men

PREEXCITATION (Wolf's parkinsinson white) SYNDROME

PREEXCITATION (WPW) SYNDROME

1. most frequently encountered type of ventricular preexcitation is that associated with AV bypass tracts
2. the most common bypass tract is an accessory atrioventricular (AV) pathway otherwise known as a Kent bundle. This is the anomaly seen in WPW syndrome. Conduction through a Kent bundle can be anterograde, retrograde, or both
3. Lown-Ganong-Levine (LGL), also has an accessory pathway (the James fibers), which connect the atria serially to the His bundle
4. The term Wolff-Parkinson-White syndrome is applied to patients with both preexcitation on the ECG and paroxysmal tachycardias. AV bypass tracts can be associated with certain congenital abnormalities, the most important of which is Ebstein's anomaly.
5. Men (60-70% cases) are affected more often than women
6. Age: Although this disease affects people of all ages, it is most commonly recognized in children and young adults presenting to the ED with a dysrhythmia. Conduction speed in the accessory pathway appears to attenuate with age.
7. Type A WPW syndrome is described as having an upright positive delta wave in all precordial leads with a resultant R greater than S amplitude in lead V1.
8. Type B has a predominantly negative delta wave and QRS complex in leads V1 and V2 and becomes positive in transition to the lateral leads resembling that of a left bundle-branch block
9. AV bypass tracts that conduct in an antegrade direction produce a typical ECG pattern of a short PR interval (<0.12>
10. LGL has a shortened PR interval due to the presence of the accessory pathway bypassing the AVN, but a normal QRS because the accessory pathway (James fibers) connects directly with the His bundle and do not depolarize the ventricles directly but do so through the typical conduction pathway through the His-Purkinje system.
11. Ecg findings

a short PR interval (0.11 s),

a wide QRS complex (0.12 s),

slurring on the upstroke of the QRS : delta wav

portal systemic anastomosis

Sites of porto caval anastamosis

(a) the gastric veins and the esophageal veins which often project as a varicose bunch into the stomach, emptying themselves into the hemiazygos vein; (b) the veins of the colon and duodenum and the left renal vein; (c) the accessory portal system of Sappey, branches of which pass in the round and falciform ligaments (particularly the latter) to unite with the epigastric and internal mammary veins, and through the diaphragmatic veins with the azygos; a single large vein, shown to be a parumbilical vein, may pass from the hilus of the liver by the round ligament to the umbilicus, producing there a bunch of prominent varicose veins known as the caput medusæ; (d) the veins of Retzius, which connect the intestinal veins with the inferior vena cava and its retroperitoneal branches; (e) the inferior mesenteric veins, and the hemorrhoidal veins that open into the hypogastrics; (f) very rarely the ductus venosus remains patent, affording a direct connection between the portal vein and the inferior vena cava.Collateral venous circulation to relieve portal obstruction in the liver may be effected by communications between (a) the gastric veins and the esophageal veins which often project as a varicose bunch into the stomach, emptying themselves into the hemiazygos vein; (b) the veins of the colon and duodenum and the left renal vein; (c) the accessory portal system of Sappey, branches of which pass in the round and falciform ligaments (particularly the latter) to unite with the epigastric and internal mammary veins, and through the diaphragmatic veins with the azygos; a single large vein, shown to be a parumbilical vein, may pass from the hilus of the liver by the round ligament to the umbilicus, producing there a bunch of prominent varicose veins known as the caput medusæ; (d) the veins of Retzius, which connect the intestinal veins with the inferior vena cava and its retroperitoneal branches; (e) the inferior mesenteric veins, and the hemorrhoidal veins that open into the hypogastrics; (f) very rarely the ductus venosus remains patent, affording a direct connection between the portal vein and the inferior vena cava.