Isolated alternans of the ST segment and T wave also may occur. T wave alternans can be macroscopic or microvolt T wave alternans which can be detected only with special equipment. ST segment and T wave alternans have been reported in vasospastic angina and is thought to be the harbringer of life threatening arrhythmias. T wave alternans (both macroscopic and microvolt) have also been linked with ventricular arrhythmias and sudden cardiac death. T wave alternans has been noted in congenital long QT syndrome preceding torsades des pointes.

In the seminal paper Lown B et al observed that out of the 200 patients with short PR interval, 23 had paroxysmal tachycardia (11%), compared with 0.5 to 1% in a control group of 200 patients with normal PR interval. Among their group of 200 patients with short PR interval 184 had normal QRS complexes and 16 had WPW pattern. The incidence of tachycardia was 25% in those with WPW pattern and 10.4% in those without a wide QRS. Of the 23 patients in their group with paroxysmal tachycardia and short PR interval, 82% had a normal QRS complex and 18% had features of WPW syndrome. They noted that those with short PR interval, normal QRS and paroxysmal tachycardia (LGL syndrome) were predominantly females. The tachycardia in half of them started in the fourth decade of life.

Holt-Oram syndrome is inherited in an autosomal dominant pattern and the mutation is in the transcription factor TBX5. The mutation was described by Li QY et al in 1997 [Li QY, Newbury-Ecob RA, Terrett JA, Wilson DI, Curtis AR, Yi CH, Gebuhr T, Bullen PJ, Robson SC, Strachan T, Bonnet D, Lyonnet S, Young ID, Raeburn JA, Buckler AJ, Law DJ, Brook JD. Holt-Oram syndrome is caused by mutations in TBX5, a member of the Brachyury (T) gene family. Nat Genet. 1997 Jan;15(1):21-9]. Though the most common cardiac anomaly is atrial septal defect of the secundum variety, other defects like ventricular septal defect have been described.Ventricular septal defect is of the muscular or trabecular variety. Cardiac malformations are seen in 75% of the affected family members. Carpal bone abnormalities are seen in all affected individuals, though it may be clinically silent and evident only radiologically.

Since it is an autosomal dominant mode of transmission, offspring have a 50% chance of being affected. But about 85% of cases of Holt-Oram syndrome have de novo mutations. Mutations in TBX5 account for upto 70% of cases of Holt-Oram syndrome.

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Colour Doppler of mitral flow on echocardiography with colour flow mapping (CFM) from the apical four chamber view. The left frame is in diastole when the mitral valve is open and there is a forward flow from the left atrium into the left ventricle. The flow is predominantly reddish, though there is an area of variance in the middle with yellowish and greenish colour. This indicates that the flow velocity in that region is above the Nyquist limit, which in this case is 61 cm/s as seen from the colour bar at the top right corner. The right frame shows the mitral valve in a closed position indicating systole and there is a small regurgitant jet of high velocity which is bluish mosaic coloured. Bluish colour indicates a reverse flow away from the transducer. The flow is from the left ventricle to the left atrium. The jet area is quite small compared to that of the left atrium, indicating that the volume of regurgitation is low. There is no significant dilatation of the left atrium or the left ventricle as the regurgitation is not sufficient to produce volume overloading of the left sided chambers.

Systolic and diastolic frames from apical 4C view on echocardiography

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Systolic and diastolic frames from apical 4C view on echocardiography seen on the same screen.The left image is in diastole as the mitral valve is seen to be open (only anterior mitral leaflet is visible as jutting into the left ventricle). In the right image, the mitral valve is seen in closed position, separating the left ventricle above and the left atrium below. Part of the septal tricuspid leaflet is also seen in the closed position. See that there is a short separation between the septal attachements of the mitral and tricuspid leaflets. This region is known as the atrioventricular septum. Atrioventricular septum is absent in endocardial cushion defects and the two septaly attached leaflets will be at the same level. A defect in the atrioventricular septum is called as a Gerbode ventricular septal defect (Gerbode VSD). In Ebstein’s anomaly the separation between the mitral and tricupsid attachments are increased so that the septal tricuspid leaflet is displaced distally. The green tracing at the bottom of the image is the ECG for identifying the frames as systolic and diastolic, when there is a doubt. Usually systolic and diastolic frames are captured for measuring the ventricular volume and ejection fraction by the area length / Simpson’s method.

Ebstein’s anomaly has been associated with maternal intake of lithium during pregnancy. Right sided accessory pathways are seen in Ebstien’s anomaly of the tricuspid valve. A similar anomaly of the left sided AV valve has been associated with congenitally corrected transposition of the great arteries. The tricuspid valve in Ebstein’s anomaly can have tricuspid stenosis, regurgitation or a combination of both together. Associated atrial septal defect can cause a right to left shunt and cyanosis.

Clinically they have multiple heart sounds due to split first and second heart sound. A superficial scratchy tricuspid murmur is also often heard. ECG shows splintered polyphasic QRS complexes, tall P waves (Himalyalan P waves) and sometimes features of pre-excitation and atrioventricular re-entrant tachycardia. X-ray chest shows the huge right atrial enlargement, which can be confirmed by echocardiography. M-mode echo shows the delay between the mitral and tricuspid valve closures. Both valves are imaged in the same parasternal view in Ebsteins anomaly. The distal displacement of the septal tricuspid leaflet is the characteristic echocardiographic finding in Ebstein’s anomaly.

Hypovolemia
Hypoxia
Hydrogen ions (acidosis)
Hypothermia
Hyperkalemia or Hypokalemia
Hypoglycemia
Toxins
Tamponade, cardiac
Tension pneumothorax
Thrombosis (Myocardial infarction / Pulmonary embolism)
Trauma

Pulseless electrical activity is treated like a cardiac arrest with cardiopulmonary resuscitation (CPR) after a quick evaluation for the reversible causes. Bedside echocardiography is useful in confirming cardiac tamponade, which should prompt immediate pericardiocentesis. Echocardiography will also show features of right ventricular enlargement and pulmonary hypertension in pulmonary embolism. Mechanical complications of a myocardial infarction can also be sought on echocardiography.

An intercostal drain is inserted in case of tension pneumothorax. Intravenous access for correction of hypovolemia and administration of drugs is of top priority. Epinephrine, vasopressin and atropine are the important drugs which may be given. Intubation and ventilation with 100% oxygen is useful in correcting the hypoxia.

Levophase of left coronary angiogram showing the coronary sinus and its tributaries. Levophase of the angiogram is obtained when you continue the cine recording till the contrast passes from the arterial tree through the capillaries to the venous system. Levophase angiogram gives an outline of the coronary sinus and its major tributaries. But it will not be enough for an excellent visualisation of the venous anatomy for left ventricular lead placement for cardiac resynchronization therapy (CRT). While planning to locate a good vein for CRT, coronary sinus angiography is directly performed by retrograde cannulation of the coronary sinus ostium from the right atrium. Care is needed to avoid dissection of the coronary sinus or its tributaries which are thin walled structures compared to the coronary arteries. Since the flow in the venous system is against the direction of contrast injection, proximal balloon occlusion is needed for good visualisation of the tributaries of the coronary sinus. The tributaries seen here are the middle cardiac vein (Middle cardiac V) and the lateral marginal vein (Lateral marginal V). The catheter tip of left Judkins catheter introduced via the transfemoral route is engaging the ostium of the left main coronary artery (LMCA).