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The complex that wasn't there
CARDIAC CONUNDRUM
The complex that wasn’t there Imogen Mitchell, MB, BS, MRCP, FRACP, Tim McKenzie, MB, BS, FRACS, and George Nikolic´, MB, BS, FRACP, FACC, Canberra, Australia As I was walking up the stair I met a man who wasn’t there Hughes Mearns, The Psycho-ed,1 Philadelphia, 1910
T
he patient was an 80-year-old man 5 days after valve replacement for aortic stenosis. An episode of atrial fibrillation resolved spontaneously. The patient remained asymptomatic on amiodarone 400 mg daily. The electrocardiogram shown in Fig 1 was obtained because of episodes of irregular pulse. By the time it was recorded, the only irregularity was a subtle bigeminy. Alternate QRS complexes were followed by 2 humps (best seen in the rhythm strip): the proximal one from a blocked P wave, and the distal one being the peak of the T wave. Blocked atrial ectopics are not rare, especially in the presence of atrioventricular blocking agents like amiodarone. As Marriott1 aptly put it, they are “the commonest causes of pauses.”1 In this case, unexpectedly, not only were there no pauses, but the blocked P waves found themselves in short, rather than long, QRS cycles. This was most unusual. None of the authors had seen a rhythm like this before. It was as though the blocked ectopics “forced” an early sinus node discharge. Calling a beat “forced” constitutes an observation, rather than an explanation: it is “a beat or complex that is
dependent in some way on the preceding conducted beat.”2 A return to see the patient helped. Additional rhythm strips were taken (Fig 2). Fig 2 is a composite: the rhythm strip of Fig 1 has one of the additional strips superimposed on it. The superimposed strip shows a sinus beat followed by 2 premature atrial ones, with their P waves coinciding with those on the strip from Fig 1. Here, however, the first hump, a blocked P wave, is followed by a QRS complex, then by another P wave and another QRS complex. The 3 QRS complexes occurred in what appeared analogous to short cycles of Fig 1; the sinus escape cycle that followed was analogous to the long cycle in Fig 1. Now, Fig 1 itself could be interpreted: it consisted of sinus beats followed by 1 blocked and 1 conducted atrial ectopic. Ventricular bigeminy thus reflected atrial trigeminy. The QRS that wasn’t there, belonging to the blocked P wave, revealed in the superimposed upper strip, caused the conundrum. Another reason for the conundrum was that the P waves all looked the same or similar. The early ones were sinoatrial (sinus) extrasystoles3 or high atrial ectopics. It is often impossible for a surface electrocardiogram to tell them apart.
1
An amateur play; lines set to music in 1939 as “The Little Man Who Wasn’t There.”
REFERENCES From the Intensive Care Unit, Canberra Hospital. Reprint requests: Dr G. Nikolic´, Canberra Hospital, PO Box 11, Woden, ACT 2606, Australia. Heart Lung® 2002;31:391-2. Copyright 2002, Mosby, Inc. All rights reserved. 0147-9563/2002/$35.00 ⫹ 0 2/1/126424 doi:10.1067/mhl.2002.126424
HEART & LUNG
VOL. 31, NO. 5
1. Marriott HJL. Practical electrocardiography, 7th ed. Baltimore: Williams & Wilkins; 1983. p. 140. 2. Home Cardiographics, c/o Dr J. A. Milliken, Hotel Dieu Hospital, Kingston, Ontario, Canada. Available at: http://www. homecardiographics.com/EcgF2.html. Accessed August 12, 2002. 3. Schamroth L. Disorders of cardiac rhythm. Oxford: Blackwell; 1971. p. 30-2.
www.mosby.com/hrtlng
391
The complex that wasn’t there
Mitchell, McKenzie, and Nikolic´
Fig 1 Twelve-lead electrocardiogram shows long-short cycle alternation and nonspecific T wave changes.
Fig 2 Additional lead 2 strip is superimposed on original one from Fig 1.
392
www.mosby.com/hrtlng
SEPTEMBER/OCTOBER 2002
HEART & LUNG
The complex that wasn’t there Imogen Mitchell, MB, BS, MRCP, FRACP, Tim McKenzie, MB, BS, FRACS, and George Nikolic´, MB, BS, FRACP, FACC, Canberra, Australia As I was walking up the stair I met a man who wasn’t there Hughes Mearns, The Psycho-ed,1 Philadelphia, 1910
T
he patient was an 80-year-old man 5 days after valve replacement for aortic stenosis. An episode of atrial fibrillation resolved spontaneously. The patient remained asymptomatic on amiodarone 400 mg daily. The electrocardiogram shown in Fig 1 was obtained because of episodes of irregular pulse. By the time it was recorded, the only irregularity was a subtle bigeminy. Alternate QRS complexes were followed by 2 humps (best seen in the rhythm strip): the proximal one from a blocked P wave, and the distal one being the peak of the T wave. Blocked atrial ectopics are not rare, especially in the presence of atrioventricular blocking agents like amiodarone. As Marriott1 aptly put it, they are “the commonest causes of pauses.”1 In this case, unexpectedly, not only were there no pauses, but the blocked P waves found themselves in short, rather than long, QRS cycles. This was most unusual. None of the authors had seen a rhythm like this before. It was as though the blocked ectopics “forced” an early sinus node discharge. Calling a beat “forced” constitutes an observation, rather than an explanation: it is “a beat or complex that is
dependent in some way on the preceding conducted beat.”2 A return to see the patient helped. Additional rhythm strips were taken (Fig 2). Fig 2 is a composite: the rhythm strip of Fig 1 has one of the additional strips superimposed on it. The superimposed strip shows a sinus beat followed by 2 premature atrial ones, with their P waves coinciding with those on the strip from Fig 1. Here, however, the first hump, a blocked P wave, is followed by a QRS complex, then by another P wave and another QRS complex. The 3 QRS complexes occurred in what appeared analogous to short cycles of Fig 1; the sinus escape cycle that followed was analogous to the long cycle in Fig 1. Now, Fig 1 itself could be interpreted: it consisted of sinus beats followed by 1 blocked and 1 conducted atrial ectopic. Ventricular bigeminy thus reflected atrial trigeminy. The QRS that wasn’t there, belonging to the blocked P wave, revealed in the superimposed upper strip, caused the conundrum. Another reason for the conundrum was that the P waves all looked the same or similar. The early ones were sinoatrial (sinus) extrasystoles3 or high atrial ectopics. It is often impossible for a surface electrocardiogram to tell them apart.
1
An amateur play; lines set to music in 1939 as “The Little Man Who Wasn’t There.”
REFERENCES From the Intensive Care Unit, Canberra Hospital. Reprint requests: Dr G. Nikolic´, Canberra Hospital, PO Box 11, Woden, ACT 2606, Australia. Heart Lung® 2002;31:391-2. Copyright 2002, Mosby, Inc. All rights reserved. 0147-9563/2002/$35.00 ⫹ 0 2/1/126424 doi:10.1067/mhl.2002.126424
HEART & LUNG
VOL. 31, NO. 5
1. Marriott HJL. Practical electrocardiography, 7th ed. Baltimore: Williams & Wilkins; 1983. p. 140. 2. Home Cardiographics, c/o Dr J. A. Milliken, Hotel Dieu Hospital, Kingston, Ontario, Canada. Available at: http://www. homecardiographics.com/EcgF2.html. Accessed August 12, 2002. 3. Schamroth L. Disorders of cardiac rhythm. Oxford: Blackwell; 1971. p. 30-2.
www.mosby.com/hrtlng
391
The complex that wasn’t there
Mitchell, McKenzie, and Nikolic´
Fig 1 Twelve-lead electrocardiogram shows long-short cycle alternation and nonspecific T wave changes.
Fig 2 Additional lead 2 strip is superimposed on original one from Fig 1.
392
www.mosby.com/hrtlng
SEPTEMBER/OCTOBER 2002
HEART & LUNG