Dynamic changes in the ST-T segment during sleep in ischemic heart disease

Dynamic Changes in the ST-T Segment During Sleep in Ischemic Heart Disease

SHLOMO STERN, MD, FACC DAN TZIVONI, MD

Jerusalem, Israel

The electrocardiographic pattern during sleep was recorded in 140 patients with chronic ischemic heart disease by the Holter continuous recording system. Among the 97 patients who had fixed abnormal ST-T changes during the day, the severity of the pathologic pattern decreased during sleep in 39, remained unchanged in 35 and became more marked in 23 patients. The deterioration of ST-T changes in the latter group lasted for several hours and only rarely was accompanied by chest pain that awakened the patient. Improvement in myocardial oxygen balance during sleep may explain the improvement observed in the first group, whereas greater obstruction of the coronary vessels may result in the fixed pattern of the ST-T segment observed in the second group. No satisfactory explanation was found for the deterioration of the ischemic pattern observed in the third group.

C h a n g e s in c a r d i o v a s c u l a r function during sleep, p r i m a r i l y a decrease in h e a r t rate a n d systolic blood pressure, have been descr!bed by K a t s c h a n d R a n s d o r f 1 a n d Boas et al. 2,a Previous reports of elect r o c a r d i o g r a p h i c changes during sleep were limited to observations of P - R a n d Q - T intervals, 4,~ a n d did not discuss nocturnal changes in the S T - T segment, p r o b a b l y b e c a u s e continuous 24 hour recordings were not o b t a i n a b l e until the d e v e l o p m e n t of a reliable s y s t e m such as t h a t of Holter. 6-s T h i s report describes our findings in 140 p a t i e n t s with ischemic h e a r t disease whose e l e c t r o c a r d i o g r a m s were studied by continuous 24 hour recording. T h i s p r o c e d u r e enabled us to c o m p a r e the diurnal a n d n o c t u r n a l S T - T s e g m e n t p a t t e r n s a n d to d e t e r m i n e whether the e l e c t r o c a r d i o g r a m r e m a i n s c o n s t a n t during sleep in these patients. In a previous s t u d y 9 of p a t i e n t s with n o r m a l electrocardiograms, we found no changes during sleep.

Materials and Methods

From the Cardiology Service, Cardiac Station for Diagnosis and Follow-up and Department of Medicine A, Hadassah University Hospital and Hebrew University-Hadassah Medical School, Jerusalem, Israel. This investigation was supported by a grant from Nessim David Gaon Of Geneva, Switzerland. Manuscript accepted January 19, 1973. Address for reprints: Shlomo Stern, MD, The Cardiology Service, Hadassah University Hospital, P.O. Box 499, Jerusalem, Israel.

One-hundred and forty patients (90 men and 50 women) with ischemic heart disease were studied. The diagnosis was based on one or more of the following criteria: history of myocardial infarction, typical anginal pain, electrocardiographic changes at rest or positive exercise test. The ages of the patients ranged between 40 and 71 years (average age 52 years). No patient had congestive heart failure or was receiving digitalis, and none was given any drugs on the day of monitoring. In most cases the electrocardiogram was recorded while the patient performed normal, everyday activities. A few patients were hospitalized, but none was bedridden. Forty-two normal subjects with no clinical or electrocardiographic evidence of cardiovascular disease were also studied. The Electrocardiocorder 350 E (Avionics), which includes a magnetic tape recorder with rechargeable batteries, was used. The batteries and tape were replaced after 12 hours. Three nonpolarizable compressed pellet silversilver chloride electrodes (Mannen-Greatbatch) were attached to the chest, which was shaved in all male patients. The exploring electrode was placed

July 1973 The AmericanJournalof CARDIOLOGY Volume32

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ST-T SEGMENT IN ISCHEMIC HEART DISEASE--STERN AND TZIVONI

FIGURE 1. Electrocardiograms obtained during a typical part of the day (top panel), during effort (center panel) and during sleep (bottom panel).

in the conventional V~ position, the ground electrode was attached to the manubrium sterni and the negative electrode was placed at the right sternal border in the fourth intercostal space. The electrocardiographic complexes obtained in this manner resembled those of lead V~, which is considered the most sensitive lead for demonstrating ST-T changes, x° Control tracings were recorded with the patient in the erect and supine positions. After 24 hours of recording, all subjects were interviewed about cardiac symptoms. The magnetic tapes were interpreted with the aid of the Electrocardioscanrmr (Avionics) and ambiguous sections of the tape were transferred to standard electrocardio•graphic paper for detailed interpretation. A n improved technique enabled immediate printout. ~ The recording system was tested for accuracy in reproduction of the S T - T segment and was found to be reliable.~2 The data ~'"

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July 1973

The American Journal of CARDIOLOGY

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Results T h e 42 n o r m a l subjects had no S T - T changes during the day or night. Of the 140 patients with ischemic h e a r t disease, 22 had n o r m a l S T - T p a t t e r n s during the day, 21 had t r a n s i e n t changes and 97 had p e r m a n e n t pathologic S T - T segments during the day. Changes during s l e e p - - e i t h e r i m p r o v e m e n t or d e t e r i o r a t i o n - - w e r e observed in 76 of the 140 patients studied. N o r m a l S T - T p a t t e r n t h r o u g h o u t sleep: This p a t t e r n was observed in all 22 patients who had normal S T - T segments during the day and in 7 of the

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described were derived in each instance from the printout of the electrocardiogram, and visual scanning was not used for a final diagnosis.

Volume 32

FIGURE 3. Electrocardiograms obtained during the day, showing permanent ST-T changes (lop panel), and during sleep (bottom panel), showing more marked ST-segment depression and T wave inversion.

ST-T SEGMENT

patients who had transient S T - T changes during the day on exertion. Fixed pathologic S T - T p a t t e r n t h r o u g h o u t sleep: In 35 patients the persistent pathologic ST-T pattern observed during the day remained unchanged during sleep. Deterioration of the S T - T p a t t e r n d u r i n g sleep: Fourteen patients who had transient S T - T changes during the day only on exertion had more pronounced and more prolonged S T - T changes during sleep (Fig. 1). Similarly, more marked S T - T depressions and further inversion of T waves were observed during sleep in 23 of those patients who also had permanent ischemic ST-T changes during the day. In 20 of these patients there was further ST-T segment depression together with inversion of T waves (Fig. 2 and 3); in 3 patients the deterioration during sleep was expressed in T wave inversion alone (Fig. 4). The deterioration in the S T - T pattern in these patients lasted for 1 to 3 hours and in some patients for as long as 5 hours. Only 2 patients were awakened by precordial pain; the others slept apparently undisturbed and did not recall nightmares or other stressful factors the next morning. The ischemic changes observed were not limited to a particular period of the night and appeared with similar frequency during the different hours of sleep. They were not accompanied by excessive bradycardia and, since they usually lasted several hours, they were apparently not related to a particular stage of sleep, such as the phase of rapid eye movement, for example. Improved S T - T p a t t e r n d u r i n g sleep: In 39 patients there was improvement in the ST-T pattern, and in 11 of this group the pattern returned to normal (Fig. 5).

Discussion The abnormal S T - T segment of patients with nonactive chronic ischemic heart disease is not expected to change unless there is anginal pain or some

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form of emotional or physical stress. 13 Certainly the pattern would not be expected to change during sleep. However, in our study, the pattern was unchanged at night in only 35 percent of patients. In 40 percent of the patients with fixed ST-T segment changes during the day, the severity of the changes decreased during sleep. In these patients the balance between oxygen supply and oxygen requirement of the myocardium during sleep may have shifted in favor of the former. This improved balance may have resulted from a smaller decrease in coronary than in systemic blood flow during sleep. The level of coronary blood flow depends mainly on the level of diastolic pressure 14 which changes little during sleep. On the other hand, the level of systemic flow shows a greater reduction during sleep since it is primarily affected by systolic and arterial mean pressures. Consequently, the myocardium, with a decreased load due to reduced demand, receives a relatively higher portion of the cardiac output, reflected in the electrocardiogram by improvement in the ST-T pattern. A certain analogy can be drawn between patients with labile hypertension whose blood pressure approaches normal during sleep and who therefore have a better prognosis and our patients with labile ST-T patterns. In the latter group, the course of ischemic disease may be milder than in patients with fixed abnormal ST-T patterns, whose oxygen balance may not improve during sleep because there is greater obstruction of the coronary vessels. The 25 patients with deterioration in the ST-T pattern during sleep are of particular interest. Although nocturnal angina often occurs during the later stages of ischemic heart disease the patient usually awakens during such attacks. In this group only 2 patien.ts awakened because of chest pail~ at the time of the ST-T changes; in the other 23 patients the prolonged ST-T changes occurred during undisturbed sleep. In some of the patients the noc-

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F I G U R E 5. E l e c t r o c a r d i o g r a m s obtained during the day (top panel), s h o w i n g S T - s e g m e n t depression, and during sleep (bottom panel), s h o w i n g return to normal pattern.

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of C A R D I O L O G Y

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ST-T SEGMENT IN ISCHEMIC HEART DISEASE--STERN AND TZIVONI

turnal electrocardiographic changes were even more pronou, nced than changes accompanied by chest pain during the day. This finding may indicate the increased pain threshold during sleep or dissociation between ischemic changes in the electrocardiogram and cardiac pain. The mechanism leading to pronounced nocturnal S T - T changes is still unclear. We cannot ascribe the changes to dreaming, and they probably are not related to the depth of sleep or sleep phases, such as

the relatively short rapid eye movement phase, since they persisted for several hours and were not confined to a particular period of the night. Tachycardia or excessive bradycardia did not accompany the changes, and the slower heart rate prevailing during sleep continued during the ischemic period.

Acknowledgment We gratefully acknowledge the invaluable technical assistance of Mrs. Batia Glassman.

References 1. Katsch G, Pansdorf H: Die Schlafbewegung des Blutdrucks. Munchen Med Wschr 69:1715-1718, 1922 2. Boas EP, Goldschmidt EF: The Heart Rate. Springfield, Ill, Charles C Thomas, 1932, p 41-53 3. Boas EP, Weiss M: The heart rate during sleep. JAMA 92:2162-2168, 1929 4. Wible CL, Jenness A: Electrocardiograms during sleep and hypnosis. J Psychol 1:238-245, 1936 5. Jenness A, Wible CL: Respiration and heart action in sleep and hypnosis. J Gen Psychol 16:197-222, 1937 6. Holter NJ: New method for heart studies. Science 134:1214-1220, 1961 7. Gilson JS, Holter NY, Glascock WR: Clinical observations using the electrocardiocorder-AVSEP continuous electrocardiographic system. Tentative standards and typical patterns. Amer J Cardiol 14:204-217, 1964 8. Stern S, Ben-Shachar G, Tzivoni D, et al: Detection of tran-

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9. 10. 11. 12. 13. 14.

sient arrhythmias by continuous long-term recording of electrocardiograms of active subjects. Israel J Med Sci 6:103-112, 1970 Tzivoni D, Stern S: Electrocardiographic changes during sleep in normal individuals (abstr). Clin Res 20:401, 1972 Blackburn H, Katigbak R: What electrocardiographic leads to take after exercise. Amer Heart J 67:184-185, 1964 Tzivoni D, Stern S: Improved method of operating the Holter-Avionics ECG recording system. Amer Heart J 83:846847, 1972 Stern S, Tzivoni D: The reliability of the Holter-Avionics system in reproducing the ST-T segment. Amer Heart J 84:427-428, 1972 Friedberg CK: Diseases of the Heart. Philadelphia and London, third edition. WB Saunders, 1966, p 729-730 Davson H, Eggleton MC: Principles of Human Physiology, 14th edition. London, J & A Churchill, 1968, p 182