Concealed atrial bigeminy and trigeminy

J. ELECTROCARDIOLOGY 11 (2), 1978, 185-189

Concealed Atrial Bigeminy and Trigeminy BY MATTHEW N. LEVY, M.D., NICHOLAS KERIN, M.D. AND MELVYN RUBENFIRE, M.D. (with the a s s i s t a n c e of PHILIP GOLDMAN)

sinus beats in a given interectopic i n t e r v a l , and n is a n y positive integer. The o t h e r form, so-called concealed t r i g e m i n y , consists of a p a t t e r n of v e n t r i c u l a r e x t r a s y s t o l e s such t h a t the n u m b e r s of conducted sinus beats in consecutive i n t e r e c t o p i c i n t e r v a l s satisfies t h e e q u a t i o n S = 3n-1; i.e., S = 2, 5, 8, 11, 14, etc. Such forms of concealed v e n t r i c u l a r e x t r a s y s toles h a v e b e e n r e p o r t e d s u b s e q u e n t l y by several o t h e r groups of investigators, and c e r t a i n v a r i a n t s h a v e been d e s c r i b e d 2 -12 However, to our k n o w l e d g e concealed a t r i a l e x t r a s y s t o l e s h a v e not y e t been reported. The p r e s e n t report describes such a n a t r i a l a r r h y t h m i a in two p a t i e n t s in each of w h o m the electrical activity of t h e h e a r t (lead V2) h a d b e e n recorded on m a g n e t i c tape for 24 hours.

SUMMARY Patterns indicative of concealed atrial extrasystoles were observed in two patients with frequent premature atrial depolarizations. In the first patient, the predominant pattern was such that most of the numbers (S) of sinus P waves between atrial extrasystoles satisfied the equation S = 3n-l, where n is any p o s i t i v e i n t e g e r . This pattern is characteristic of concealed trigeminy. Over a sequence of 49 interectopic intervals, this patient vacillated b e t w e e n concealed atrial trigeminy and bigeminy. A second patient displayed a pattern characteristic of the "even number" variant of concealed bigeminy. The numbers of sinus P waves in consecutive interectopic intervals were predominantly even. These various patterns of concealed atrial extrasystoles closely resemble previously reported patterns of concealed ventricular extrasystoles. Concealed v e n t r i c u l a r e x t r a s y s t o l e s were o r i g i n a l l y d e s c r i b e d b y S a t o u et al 1 a n d S c h a m r o t h a n d M a r r i o t t . 2-4 Two p r i n c i p a l forms of this a r r h y t h m i a h a v e b e e n described. One form, so-called concealed b i g e m i n y , is c h a r a c t e r i z e d by a n odd n u m b e r of conducted sinus beats b e t w e e n extrasystoles; i.e., S = 2 n - l , w h e r e S is t h e n u m b e r of c o n d u c t e d

CASE REPORTS Case I. T h e first p a t i e n t was a 77 y e a r old w o m a n in w h o m f r e q u e n t p r e m a t u r e b e a t s w e r e d e t e c t e d on p h y s i c a l e x a m i n a t i o n . A H o l t e r r e c o r d i n g was o b t a i n e d and long segm e n t s were p l a y e d back for detailed analysis. The most c h a r a c t e r i s t i c p a t t e r n of occurrence of the a t r i a l e x t r a s y s t o l e s is shown in Fig. 1. T h e strips are c o n t i n u o u s , a n d t h e p r e m a t u r e a t r i a l d e p o l a r i z a t i o n s a r e indic a t e d by t h e a r r o w s . T h e n o r m a l s i n u s P waves were all u p r i g h t , w h e r e a s the p r e m a t u r e P waves were inverted. The P'-R intervals for t h e p r e m a t u r e depolarizations w e r e equal to or longer t h a n the P-R i n t e r v a l s for the n o r m a l sinus depolarizations. It is likely, therefore, t h a t the locus of origin of the prem a t u r e depolarizations was superior to the A-V node. T h e coupling i n t e r v a l s (P-P') varied from 0.53 to 0.73 sec. T h e interectopic i n t e r v a l s w e r e not m u l t i p l e s of a n y l e a s t c o m m o n value, and fusion P waves were not observed. Therefore the arrhythmia was probably not a n atrial p a r a s y s t o l e . The n u m b e r s (S) of n o r m a l sinus P waves in the interectopic i n t e r v a l s are denoted in Fig. 1 by the n u m b e r s b e t w e e n t h e arrows. It will be n o t e d t h a t e a c h v a l u e c o n f o r m s to t h e

From the Department of Investigative Medicine, Mt. Sinai Hospital of Cleveland Ohio, and the Section of Cardiovascular Diseases, Department of Medicine, Sinai Hospital of Detroit, Michigan. This work was supported by U.S. Public Health Grant HL-10951. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked ~'advertisement" in accordance with 18 U.S.C. w1734 solely to indicate this fact. Reprint requests to: Matthew N. Levy, M.D., Department of Investigative Medicine, Mt. Sinai Hospital, 1800 E. 105 St., Cleveland, OH 44106. 185

186

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1

,

,

1

1

,

I

, ,

1

11

,

1 ,

l

1

. I

I 5

1

1

2 sec. I

Fig. 1. Rhythm strip played back from a Holter monitor recording from a patient (Case I) with frequent atrial extrasystoles (denoted by the arrows). The numerals between the arrows indicate the numbers of sinus P waves between consecutive extrasystoles. All numbers (S) fit the equation S = 3n-1, which characterizes concealed trigenimy (n is any positive integer). The strips are continuous. This rhythm strip was recorded at 9:22 P.M. (Table 1). (QRS complexes retouched)

equation S = 3 n - 1 , which is characteristic of c o n c e a l e d t r i g e m i n y . The c o n t i n u o u s r h y t h m strip shown in the figure was t a k e n from a sequence of 19 consecutive interectopic intervals. The values of S for 17 of the 19 intervals conformed to the equation S = 3 n - 1. The binomial distribution 13 was used to test the null hypothesis t h a t there is an equal l i k e l i h o o d t h a t S -- 3n, S = 3 n - l , and S = 3 n - 2 ; i.e., on the basis of chance alone,

TABLE I Distribution of the Numbers of Sinus P Waves (S) in a Patient (Case I) with Frequent Premature Atrial Depolarizations

S

Number

1 2

0 47

3 4 5

1 2 26

6

3

7

0

8

2

9 10 11

1 1 4

S

Number

12 13 14

2 0 2

15 16

1 0

17

0

24

1

3n-1

82 93

Total P

10 -4g

only one-third of the values of S would satisfy the equation S = 3 n - 1. The probability t h a t 17 out of 19 consecutive values of S would satisfy this equation on the basis of chance alone is extremely small (P = 10-6). Sequences from three other segments of this patient's electrocardiogram (ECG) were also analyzed in a similar manner. The composite data from the four sequences are compiled in Table 1. Of the 93 interectopic intervals analyzed, 82 conformed to the equation for concealed trigeminy. The probability t h a t such a distribution could occur by chance alone is infinitesimally small (P = 10-49). The tendency to conform to the equation for concealed trigeminy was greater the smaller the value of S; i.e., the more frequent the a t r i a l extrasystoles. Conversely, the more widely spaced the extrasystoles, the greater was the apparent tendency for the values of S not to obey the e q u a t i o n S = 3 n - 1 . For example, for those values of S > 5, there were eight values of S t h a t conformed to the equation, and nine values that did not. On the other hand, for values of S ~< 5, there were 73 values of S t h a t did conform, and only 3 t h a t did not. In m a n y segments of the magnetic tape record, atrial extrasystoles were absent or very infrequent. In such segments, the heart rate tended to be appreciably slower t h a n in those where atrial extrasystoles were abundant. In approximately h a l f the segments where n u m e r o u s extrasystoles occurred, the patterns resembled those compiled in Table 1 and shown in Fig. 1; i.e., a pattern of concealed J. ELECTROCARDIOLOGY, VOL. 11, NO. 2, 1978

CONCEALED ATRIAL EXTRASYSTOLES

1

,

l

187

,

1

is

I

2 sec.

1

I

Fig. 2. Another segment obtained from the magnetic tape record of Case I. The numbers of sinus P waves between atrial extrasystoles (denoted by the arrows) are all odd, which is characteristic of concealed atrial bigeminy (classical form). The strips are continuous, and were recorded at 6:54 P.M. This strip includes the last value in column 4 and the first five values in column 5 of Table 2. (QRS complexes retouched)

t r i g e m i n y . In most of the r e m a i n i n g segments, no definite pattern could be discerned; i.e., the distribution of extrasystoles appeared to be random. In one segment (6:54 P.M.), however, the p a t t e r n appeared to vacillate between concealed b i g e m i n y and concealed t r i g e m i n y . The consecutive values of S for this segment are compiled in Table 2. The values of S are subdivided arbitrarily into five columns, but the columns are continuous. Each new column was begun at a point at which it appeared t h a t a shift in r h y t h m had occurred. Thus, in columns 1, 3, and 5, the values of S appear to conform to the equation for concealed bigeminy, S = 2 n - l ; i.e., almost all values are odd. Of the total number of 24 interectopic intervals included in columns 1, 3, and 5, 21 of the values of S were odd, and only t h r e e were even (P = 10-4). On the other hand, in columns 2 and 4, all 25 of the v a l u e s satisfied the e q u a t i o n , S = 3 n - 1 (P = 10-12). A segment of this record, extending from the last interectopic interval in column 4 and including the first five intervals in column 5, is shown in Fig. 2. Thus, in the segment recorded at 6:54 P.M. (Table 2), the r h y t h m vacillated between concealed b i g e m i n y a n d concealed t r i g e m i n y . The precise points of transition were not always clear, because some values of S (notably S = 5) are common to both rhythms. Also, the sinus rate was not significantly different among the sections of the record corresponding to t h e v a r i o u s c o l u m n s in t h e table. Hence, shifts between concealed bigeminy and concealed trigeminy did not appear to be induced by changes in the heart rate. Case II. The second patient was a 68 year old m a n who complained of pain on exertion. FreJ. ELECTROCARDIOLOGY, VOL. 11, NO. 2, 1978

quent premature beats were noted, and so a Holter tape recording was obtained. N u m e r o u s p r e m a t u r e a t r i a l depolarizations, with bizarre QRS complexes denoting a b e r r a n t v e n t r i c u l a r conduction, were observed periodically t h r o u g h o u t the record. Between such stretches with frequent premature atrial depolarizations, there were long intervals during which a normal sinus r h y t h m prevailed. In some periods with frequent premature depolarizations, the atrial

TABLE II Consecutive Values of the Numbers of Sinus P Waves Between Atrial Extrasystolesin Case I at Time 6:54 P.M. Each Column is a Continuation of the Preceding Column.

2n-1 Total 3n-1 Total p

1

2

3

4

5

5 5 13 2 5 5 9 9

5 2 5 5 5 5 2 2 2 2 5 5 2 5

10 7 3 3 3 3

5 5 2 5 2 5 11 5 2 5 5

7 15 3 5 3 5 3 2 5 3

7 8

10-2

5 6 14 14 10-7

10-1

9 10 11 11 10-5

10-2

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LEVY ET AL

6

6

1

4

1

1

8

I

2 sec.

I

extrasystoles seemed to occur randomly. The interectopic intervals did not appear to be simple multiples of some least common interval, however, and atrial fusion beats were not evident. In numerous sections of the record, the extrasystoles occurred r e g u l a r l y after every fourth sinus P wave (quintageminal pattern; S = 4). Throughout the record, the coupling intervals were constant at 0.40 sec., no m a t t e r whether the pattern of occurrence of extrasystoles was random or regular. In three sections of the record, the predomi n a n t value of S was 4, but other values of S were also abundant. The majority of such values were even; i.e., S = 2n. A short section of the ECG is shown in Fig. 3. Of the 54 consecutive interectopic intervals analyzed, 49 of t h e m contained an even number of sinus P waves. The probability of obtaining such a distribution on the basis of chance alone is i n f i n i t e s i m a l l y small (P = 1 0 - 1 ~ Hence, this sequence of atrial extrasystoles fulfills the criterion for the "even number variant" of concealed atrial bigeminy; such a distribution has previously been described for ventricular extrasystoles. 7,s

DISCUSSION In electrocardiograms of the two patients described above, sequences of atrial extrasystoles occurred which were characteristic of patterns described previously for the ventricles. In case I, the patterns were characteristic of t h e c l a s s i c a l f o r m s of c o n c e a l e d bigeminy (Fig. 2) and concealed t r i g e m i n y (Fig. 1). In the classical form of concealed ventricu l a r b i g e m i n y (S = 2 n - 1 ) , t h e e l e c trophysiological basis for the extrasystoles h a s n o t b e e n e s t a b l i s h e d . The p r i n c i p a l hypotheses involve either a periodic discharge of an ectopic focus2-4's or a reentry phenomenon. 7 In the f o r m e r h y p o t h e s i s , classical concealed bigeminy is accounted for either by ectopic enhancement 3,4 during alternate sinus beats or by a 2:1 exit block in the "ventricular-ectopic" junction, s Conversely,

Fig. 3. A segment obtained from a Holter tape record of Case II; the strips were continuous. The numbers of sinus P waves between atrial extrasystoles are even, which characterizes the even number variant of concealed bigeminy. (QRS complexes retouched).

in the latter hypothesis, the a r r h y t h m i a is explained on the basis of a 2:1 block in a reentry loop. 7 Similarly, a 2:1 block in a reentry loop has also been proposed for the evenn u m b e r v a r i a n t (S = 2n) of c o n c e a l e d bigeminy, 7 but the occurrence of a manifest extrasystole is consistently shifted by one beat. Consequently, the numbers of normally conducted beats between extrasystoles are p r e d o m i n a n t l y even r a t h e r t h a n odd. E1Sherif et a114 have recently adduced evidence in support of the reentry mechanism in their studies ofventricular a r r h y t h m i a s in the late stages of experimental myocardial infarction. In the classical form of concealed ventricular t r i g e m i n y (S = 3 n - 1 ) , the underlying basis is probably similar to t h a t for concealed bigeminy, except t h a t the cyclic changes occur every third, rather t h a n every second, sinus beat. In concealed trigeminy, then, either the ectopic focus approaches the firing threshold every third beat, 3,4 or a 3:1 block is present in a ventricular-ectopic junction or in a reentry loop. s,lo At present, it cannot be determined which, if any, of the above hypotheses are correct. In our first case, the coupling intervals were variable, an observation t h a t tends to favor an ectopic focus origin. Conversely, the coupling intervals were constant in the second patient; this tends to favor a r e e n t r y mechanism. However, there is a b u n d a n t evidence to show t h a t fixed coupling may occur during the repetitive firing of an ectopic focus, and t h a t reentry m a y be associated with variable coupling. The complexity of the problem has been discussed in detail in the recent incisive paper by Moe et al. 15 The patterns of atrial extrasystole distribution in the two cases described in this report resemble very closely those previously reported for ventricular extrasystoles. It is likely, therefore, t h a t whatever proves to be the true mechanism responsible for concealed ventricular extrasystoles, a similar mechanism probably also operates for concealed atrial extrasystoles. For those atrial extrasystoles t h a t occur on J. ELECTROCARDIOLOGY, VOL. 11, NO. 2, 1978

CONCEALED ATRIAL EXTRASYSTOLES

the basis of reentry, the reentry loop might include either the A-V junction or the S-A node. The p a t h w a y for reentrant ventricular extrasystoles m a y also include the A-V junction, but this probably occurs more commonly with atrial extrasystoles. Manifest atrial extrasystoles usually reset the sinus r h y t h m , whereas manifest ventricular extrasystoles usually do not. Hence, there are significant differences in timing between c o n s e c u t i v e e x t r a s y s t o l e s , d e p e n d i n g on which chambers are involved. In concealed ventricular trigeminy, for example, the time from an exciting ventricular depolarization of sinus origin t h a t gives rise to a manifest extrasystole till the next exciting ventriclar depolarization (that gives rise to either a manifest or a concealed extrasystole) would be equal to the length of three sinus cycles. On the other hand, in concealed atrial trigeminy, the time from an exciting atrial depolarization of sinus origin t h a t gives rise to a manifest extrasystole till the next exciting atrial depolarization ( t h a t gives rise to either a manifest or a concealed extrasystole) would be e q u a l to less t h a n t h r e e s i n u s cycle lengths, if the manifest extrasystole resets the sinus rhythm. In our patient with concealed atrial trigeminy, the manifest atrial extrasystoles did reset the sinus r h y t h m (Fig. 1). Nevertheless, the numbers of sinus depolarizations (S) between manifest extrasystoles still conformed to the same f o r m u l a (S = 3 n - 1) for concealed trigeminy t h a t also characterizes concealed ventricular extrasystoles.

2.

3. 4. 5. 6. 7. 8. 9. 10. 11.

12. 13. 14.

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