An Unusual Case of Syncope

Clinical History

This is a 73 year old man who had a previous aortic valve replacement with known depressed left ventricular ejection fraction of 30%. He had a history of prior syncopal episodes dating back over 10 years, with each episode occurring every 3-4 years. He was admitted to the hospital after having another episode of abrupt syncope. He awoke spontaneously and quickly with no residual symptoms as was the case with his prior episodes of syncope.

Figure 1

This figure illustrates his 12 lead electrocardiogram. He has a left bundle branch block and a first degree AV block. While on cardiac telemetry, he was noted to periods of AV Wenckebach and periods of 2:1 AV block with heart rates as low as 35 beats per minute. All of this would suggest a bradycardia (show heart rate) as the cause of his syncope.

Figure 2

Because of his abnormal ejection fraction, he was referred for invasive electrophysiologic testing. This figure demonstrates his response to pacing in the upper chambers of his heart (atria). Electrode tipped catheters are placed through the large veins in the leg and positioned in the upper and lower chambers of the heart.

When his atria are placed at a cycle length of 500 ms (120 beats per minute), he develops 2:1 AV block, such that only every other impulse gets down to the lower chambers (ventricles). His ventricular rate is thus only 60 beats per minute. Note, however, the absence of a His bundle potential in the blocked atrial beats. This indicates that the level of the block is above the level of the bundle of His, and thus, may not be a pathologic form of block.

Figure 3

With ventricular stimulation, however, the patient was found to have easily inducible ventricular tachycardia. This figure shows stimulation of the ventricles through the catheters with introduction of two early beats after an initial eight beat drive train. This protocol results in an initiation of a wide complex tachycardia.

Figure 4

This study shows the sustained tachycardia. Note that there are fewer impulses in the atrial or upper chamber recordings (labeled hRA) then in the ventricular channel recordings (labeled Rva). This indicates AV dissociation and is a diagnostic of a ventricular source of the tachycardia.

This is a potentially life threatening rhythm problem. The ability to induce this rhythm in the Electrophysiology Lab is indicative of a significant risk of spontaneous occurrence and sudden death .

On this basis, the patient went on to have a dual chamber defibrillator implanted the next day. The current generation of these devices also serve as sophisticated pacemakers that would also serve to prevent significant slow heart rhythms.

This case demonstrates the importance of a thorough evaluation in patients who have fainting spells in the setting of serious underlying heart disease.