Key words: Coarctation of the aorta â Hypertension â. Recoarctation â Exercise testing. Coarctation of the aorta (CoA) is a congenital defect with a prevalence ...
Pediatr Cardiol 17:301–307, 1996
Pediatric Cardiology © Springer-Verlag New York Inc. 1996
Exercise-Induced Hypertension After Corrective Surgery for Coarctation of the Aorta ´ . Sigurðardo´ttir,1 H. Helgason2 L.Y 1
University of Iceland, Medical School, Reykjavı´k 101, Iceland Department of Pediatrics, University Hospital of Iceland, Reykjavik 101, Iceland
2
Abstract. The purpose of this investigation was to study exercise-induced hypertension after surgical repair of coarctation of the aorta (CoA). Groups of 27 patients with CoA and 27 healthy control subjects, 6–21 years old, were exercised to exhaustion using the Bruce protocol. Fourteen patients had undergone surgery during the first year of life (group A), and 13 patients had been operated on later (group B). The pulse rate and systolic blood pressures (BP) in the arm and leg were measured before, during, and after exercise to evaluate changes in the BP and the arm/leg BP gradient with exercise. The systolic BP was significantly higher in the patients than in the controls at all stages of the exercise test (p < 0.01), as was the arm/leg BP gradient both before and after exercise (p < 0.01); the latter increased significantly with exercise in the patient group (p < 0.05). We found hypertension to be a more common and severe problem in group B patients, who had higher blood pressures than their controls at rest and during exercise (p < 0.05). Exercise-induced hypertension was also more common in group B (23%) than in group A (7%). We conclude that exercise-induced hypertension and recoarctation are problems in postoperative CoA patients. Moreover, exercise-induced hypertension is more common in patients with CoA operated on after the first year of life. Key words: Coarctation of the aorta — Hypertension — Recoarctation — Exercise testing
Coarctation of the aorta (CoA) is a congenital defect with a prevalence of 1 per 1700 children in Iceland [14]. The site of the coarctation is usually opposite the former opening of the ductus arteriosus, just distal to the left subclavian artery. The main symptom of CoA is arterial Correspondence to: H. Helgason
hypertension in the systemic circulation proximal to the coarctation, which results in premature atherosclerosis, heart failure, aneurysms, and sudden death [4]. The treatment of choice for CoA is an operation in which the coarctation segment is resected [7]. Patients who undergo an operation have higher cardiovascular morbidity and mortality than the normal population. They are thought to result from the continuous hypertension [5, 19]. The most common operations for CoA are resection of the coarctation segment with end-to-end anastomosis in older patients and subclavian flap angioplasty in infants. CoA patients in Iceland undergo one or the other of these operations, with only a few requiring further surgical intervention in the form of angioplasty because of restenosis [14]. However, even after surgery the patients are not cured: 10–30% continue to have hypertension at rest [2, 10, 16, 17, 20], and 30–65% have an abnormal blood pressure response to exercise [12, 13, 15]. The current approach is for corrective surgery to take place at the age of 4 years if the child is otherwise healthy and there is no sign of heart failure. If an infant with CoA suffers from heart failure, the operation is performed without delay as the patient’s prognosis depends on restoring normal blood flow in the aorta. Surgery during the first year of life has been thought to carry a higher risk of restenosis [24]. In this study we divided our patient group into two subgroups: group A, consisting of patients who presented with heart failure and required acute surgery; and group B, consisting of children who underwent elective surgery at a later date. The purpose of the study was to establish whether those patients operated on during infancy have a long-term outcome similar to that for those who undergo corrective surgery after 1 year of age. We recorded the endurance time and systolic blood pressure with exercise in Icelandic patients with CoA and a paired control group. The systolic blood pressure gradient between the arm and leg was also measured and its changes with exercise noted.
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Materials and Methods
Table 1. Characteristics of patients and controls
Patients
Characteristic
CoA patients
Controls
p
Age (months) Sex Weight (kg) Height (cm) BSA (m2) Maximal endurance time (min) Systolic BP (mmHg) At rest Maximum After exercise Arm/leg BP gradient At rest After exercise Pulse rate (bpm) At rest Maximum After exercise
175 ± 10 16M, 11F 54.2 ± 4.1 159.0 ± 3.7 1.53 ± 0.07
171 ± 10 16M, 11F 53.2 ± 3.6 161.3 ± 3.7 1.54 ± 0.07
0.02 NS NS NS
13.9 ± 0.4
14.1 ± 0.4
NS
Forty-two patients were diagnosed with CoA in Iceland during the years 1968–1987 [14]. Nine of these patients are now dead and 4 could not be exercise-tested because of severe disabilities. One patient could not be located, and one patient (an 18-year-old man who had recently undergone corrective surgery) was still taking a b-blocker and was excluded from the study. The study group therefore consisted of 27 patients (6–21 years old; 16 males, 11 females). They were all in good health, entirely symptom-free, and taking no antihypertensive medication.
Methods The systolic blood pressure (BP) was measured in the right arm and left calf with the subject in a supine position. The BP measurements were done with an electronic sphygmomanometer; the cuff size was chosen so it covered at least two-thirds of the upper arm or calf. A 12-lead electrocardiogram (ECG) was obtained prior to exercise and at 3-min intervals throughout the exercise test. The patient was exercise-tested according to the Bruce protocol [3], in which the speed and slope of a treadmill are increased every 3 min until the subject is exhausted. At each stage of the test the systolic BP is measured with a mercury sphygmomanometer and the pulse rate noted. When the treadmill was stopped these measurements were repeated with the patient in a supine position. The electronic sphygmomanometer was then used to measure the BP in the arm and leg as was done before exercise began. The systolic BP and the pulse rate were monitored to record the recovery phase. In addition, the maximal endurance time was measured in minutes. Comparisons were made between the patients and controls regarding: (1) maximal endurance time; (2) changes in pulse rate with exercise; (3) systolic BP; and (4) the BP gradient between the arm and leg. The patients were then divided into two groups according to when their corrective surgery took place. Group A included the patients who underwent surgery during their first year of life, and group B consisted of patients operated on later in life. These two groups were compared with each other as well as with their age- and sex-matched control groups.
Statistical Analysis Results are presented as the mean ± SEM, and the differences between groups are compared with a two-tailed t-test. When the comparison was between age- and sex-matched individuals, a paired t-test was used, whereas an unpaired t-test was used to compare group A with group B. A probability value of 200 mmHg with exercise. Sixteen patients (59%) had a positive BP gradient (2–53 mmHg) after exercise, nine of whom (33%) had a
gradient of >10 mmHg. Comparing the maximal systolic BP of these 16 individuals with their postexercise BP gradient shows a positive correlation that was not significant (r 4 0.21, p 4 0.44; Fig. 7). The BP gradient between arm and leg in the patients at rest was −2.6 ± 11.9 mmHg. It increased significantly with exercise to 6.5 ± 19.9 mmHg (p 4 0.03).
Groups A and B Versus Paired Control Groups Patient characteristics for patient subgroups and a comparison with paired control groups are shown in Table 2.
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Fig. 5. Regression analysis of the systolic blood pressure (BP) in the arm of the controls before and after exercise (r 4 0.78, p 4 0.0001)
Fig. 6. Regression analysis of a positive blood pressure (BP) gradient at rest and maximal systolic BP during exercise (r 4 0.78, p 4 0.03)
A comparison between the two patient groups is also shown. Endurance. There was no difference in maximal endurance between group A and its control group (13.5 ± 0.3 min versus 14.1 ± 0.5 min; p 4 0.33). The same was seen for group B (14.3 ± 0.7 min versus 14.1 ± 0.6 min; p 4 0.85). The endurance times for groups A and B were also similar.
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Fig. 7. Regression analysis of a positive blood pressure (BP) gradient after exercise and maximal systolic BP during exercise (r 4 0.21, p 4 0.44)
Pulse Rate. The pulse rate was comparable in the two patient groups at all stages of exercise, as it was when we compared each patient subgroup with its paired control group. When we looked at the recovery phase, however, we found a significant difference between groups A and B. The pulse rate 3 min after exercise was 97 ± 4 bpm for group A and 115 ± 4 bpm for group B (p 4 0.007). Systolic Blood Pressure. Patients in group B had higher systolic BPs than those in group A at all stages of the exercise test, though the difference was not significant. When each group was compared with its control group, however, there was a striking difference. Group B had a significantly higher systolic BP than its controls from the start of exercise, and the difference continued after the exercise was over. Systolic BP in group A, on the other hand, was similar to that in its controls until the third stage of exercise and normalized as soon as exercise was halted (Figs. 8, 9). Positive Blood Pressure Gradient. Both patient groups had a higher arm/leg BP gradient than their controls. This difference was not significant except for group A after exercise (p 4 0.005).
Discussion When surgical correction for CoA became available it was hoped that a definitive cure for the lesion had been found. Unfortunately, significant morbidity and mortal-
Sigurðardo´ttir and Helgason: Exercised-Induced Hypertension with CoA
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Table 2. Characteristics of patient subgroups and paired control groups Characteristic
p Age (months) Sex Weight (kg) Height (cm) BSA (m2) Maximal endurance time (min) Systolic BP (mmHg) At rest Maximum After exercise Arm/leg BP gradient At rest After exercise Pulse rate (bpm) At rest Maximum After exercise
Group A vs. controls
Group B vs. controls
Group A (n 4 14)
Controls for group A (n 4 14)
p
Group B (n 4 13)
162 ± 15 10M, 4F 50.1 ± 5.8 156.4 ± 5.5 1.47 ± 0.11
157 10M, 4F 49.5 157.3 1.47
± 14
0.02
± 5.1 ± 5.9 ± 0.11
NS NS NS
189 6M, 7F 58.0 161.8 1.60
± 0.5
NS
14.3
± 3 ± 3 ± 6
NS 0.003 NS
13.5 ± 0.3 123 158 139
± 4 ± 8 ± 6
−3.1 ± 3.0 9.0 ± 5.9 73 188 96
± 4 ± 3 ± 4
14.1 122 133 137
−11.8 ± 3.3 −18.9 ± 5.2
NS 0.005
68 189 93
NS NS NS
± 3 ± 2 ± 4
136 175 154
Controls for group B (n 4 13)
p
NS
NS
± 5.9 ± 4.9 ± 0.10
185 ± 12 6M, 7F 57.2 ± 4.9 165.6 ± 4.3 1.62 ± 0.09
NS NS NS
NS NS NS
± 0.7
14.1 ± 0.6
NS
NS
0.01 0.005 NS
NS NS NS
−11.4 ± 2.4 −13.6 ± 4.1
NS NS
NS NS
76 194 108
NS NS NS
NS NS 0.007
± 13
± 5 ± 11 ± 7
−1.7 ± 4.0 −2.5 ± 5.3 75 192 115
Group A vs. group B
± 4 ± 4 ± 4
125 141 142
± 4 ± 4 ± 4
± 3 ± 3 ± 5
BSA, body surface area; bpm, beats per minute; NS, not significant.
Fig. 8. Systolic blood pressure (BP) (mean ± SEM) in group A versus controls at various stages of the exercise test. Results of the t-test are shown below each stage
ity have been documented in patients who have been operated on for CoA [2, 4, 5, 10, 12, 13, 15–17, 19, 20].
Positive Blood Pressure Gradient Our results support those reported for previous studies, which showed that exercise-induced hypertension and residual obstruction with a positive arm/leg BP gradient are problems in a significant percentage of postoperative
Fig. 9. Systolic blood pressure (BP) (mean ± SEM) in group B versus controls at various stages of the exercise test. Results of the t-test are shown below each stage
CoA patients [2, 5, 10, 12, 13, 15–21]. Our patients consider themselves cured even though 18.5% of them had an arm/leg BP gradient at rest of >10 mmHg, with 33% having this high gradient after exercise as well. Daniels et al. [9] found a positive arm/leg BP gradient in 42% of their patients, and James and Kaplan [15] in 11%. All our patients with a BP gradient of >10 mmHg at rest had a positive arm/leg BP gradient after exercise. Four of fourteen patients in group A (28.6%) and five of thirteen patients in group B (38.5%) had a BP gradient of >10 mmHg after exercise. These patients
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were considered to be suffering from restenosis [11, 19], and we concluded that the rate of residual obstruction is the same regardless of whether corrective surgery takes place during infancy or later in life. Williams et al. [24] found restenosis to be more common in patients operated on when they were infants. We observed a significant rise in the arm/leg BP gradient with exercise in our patient group (p 4 0.03). In normal subjects the elasticity of the aorta helps to keep systolic BP steady despite an increase in cardiac output. In postoperative CoA patients this elasticity is reduced because of scarring of the vessel wall. These patients therefore acquire exercise-induced hypertension proximal to the lesion and a rise in the BP gradient that develops across the obstruction. Therefore we believe that restenosis can be diagnosed at an earlier stage if the arm/leg BP gradient is measured after exercise.
Endurance The patients and controls had similar endurance, results that are comparable to those of previous studies [8]. A significant proportion of our patients had an abnormal BP response to exercise, and one-third had restenosis to some degree. The patients are not aware of these developments and are as physically active as the control group. The patients in this study are still young, however, and the observation period after their operation is not sufficiently long for definitive conclusions. The main value of these measurements will therefore be when this same patient group is evaluated later in life.
Pulse Rate Exercise-induced acceleration in pulse rate was similar in the patient group and the controls in our study. A correlation between pulse rate during the second stage of exercise and maximal endurance has been found in previous studies [8]. Our results confirmed this finding in both the patient group and the controls. We therefore conclude that postoperative CoA patients have a normal accelerative response to exercise. Tachycardia does not seem to be a part of the clinical picture of restenosis. Patients in group B took significantly longer to normalize their pulse rates after the completion of exercise than did patients in group A. This finding infers that cardiac function is diminished in patients with CoA operated on after the age of 1 year.
Systolic Blood Pressure An abnormal BP response to exercise is well known in postoperative CoA patients [6, 10, 12, 13, 15, 22, 23].
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Our results are similar to those of previously published studies. The systolic BP in our patients was higher than in the controls; the difference was not significant at rest but increased with exercise. When the exercise period was completed the patients normalized their BPs quickly. Previous studies have emphasized this point [5]. The patients operated on after 1 year of age (group B) had a significantly higher systolic BP than their control group at rest. Patients in group A, on the other hand, were normotensive until the second stage of exercise. This finding supports our belief that patients who undergo corrective surgery after the age of 1 year have a higher probability of continuous hypertension and are in more danger of developing long-term complications of the CoA than are those operated on during infancy. The correlation in our study between a positive arm/ leg BP gradient and exercise-induced hypertension is significant (r 4 0.75; p 4 0.02). Exercise-induced hypertension correlates with a positive arm/leg BP gradient, which in turn is associated with restenosis. The correlation between these factors is so strong that we believe it essential to consider performing angiography with an invasive measurement of the BP gradient in postoperative CoA patients who have considerable exerciseinduced hypertension. If a restenosis is found, it can then be dilated. Four patients developed severe hypertension with exercise (210–265 mmHg). Three of these patients were from group B (23%) compared with one patient from group A (7%). We therefore do not agree with Williams et al. [24], who found 27% of children operated on during infancy to be hypertensive later in life. Our results are in concordance with those of Barratt-Boyes [1], although his patients were older than those in our group. He concluded that corrective surgery should be done as soon as possible. The arm/leg BP gradient increases significantly with exercise. The increase consists of two factors: (1) an increase in systolic BP in the arm and (2) lowering of the systolic BP in the leg. This BP drop is probably due to obstruction in blood flow to the lower extremities. Another proposed mechanism is that patients with CoA do not have normal vasodilatation with exercise. Hypertension proximal to the obstruction can lead to faulty autoregulation even though vasodilatation is normal distal to the obstruction.
Conclusions A considerable proportion of postoperative CoA patients in Iceland have exercise-induced hypertension or some degree of restenosis. We find exercise testing an efficient method for monitoring the follow-up of these patients. We emphasize the need to measure the systolic BP during exercise and to measure the arm/leg BP gradient at
Sigurðardo´ttir and Helgason: Exercised-Induced Hypertension with CoA
rest. These measurements seem to detect abnormalities early, at a time when the patients consider themselves completely healthy. Such diagnostic practice can help us identify those patients in need of more extensive followup and perhaps in need of medical therapy or dilatation at the site of the coarctation. We also conclude that patients who undergo corrective surgery after the age of 1 year are at greater risk of hypertension. Hence we believe that corrective surgery for CoA should take place at the first convenient time after diagnosis, preferably before the child’s first birthday. Acknowledgment. This study was supported by a grant from the University of Iceland Research Fund.
References 1. Barratt-Boyes B (1985) Surgical coarctation of the aorta: a review of 30 years of experience. Trans Coll Med S Afr 6:25–42 2. Bergdahl L, Bjork VO, Jonasson R (1983) Surgical correction of coarctation of the aorta: influence of age on late results. J Thorac Cardiovasc Surg 85:532–536 3. Bruce RA, Kusumi F, Hosmer D (1973) Maximal oxygen intake and normographic assessment of functional aerobic impairment in cardiovascular disease. Am Heart J 85:546–560 4. Campbell M (1970) Natural history of coarctation of the aortae. Br Heart J 32:633–640 5. Clarkson PM, Nicholson MR, Barratt-Boyes BG, et al (1983) Results after repair of coarctation of the aortae beyond infancy: a 10–28 year follow-up with particular reference to late systemic hypertension. Am J Cardiol 51:1481–1488 6. Connor TM, Baker WP (1981) A comparison of coarctation resection and patch angioplasty using post exercise blood pressure measurements. Circulation 64:567–572 7. Crafoord C, Nylin G (1945) Congenital coarctation of the aorta and its surgical treatment. J Thorac Cardiovasc Surg 14:347–361 8. Cumming GR, Everatt D, Hastman L (1978) Bruce treadmill in children: normal values in a clinic population. Am J Cardiol 41: 69–75 9. Daniels SR, James FW, Loggie JMH, et al (1987) Correlates of resting and maximal exercise systolic blood pressure after repair of coarctation of the aorta: a multivariable analysis. Am Heart J 113: 349–353
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10. Earley A, Joseph MC, Shinebourne EA, et al (1980) Blood pressure and effects of exercise in children before and after surgical correction of coarctation of aorta. Br Heart J 44:411–415 11. Eshaghpour E, Olley PM (1972) Recoarctation of the aorta following coarctectomy in the first year of life: a follow up study. J Pediatr 80:809–814 12. Freed MD, Rocchini A, Rosenthal A, et al (1979) Exercise induced hypertension after surgical repair of coarctation of the aorta. Am J Cardiol 43:253–258 13. Hanson E, Erikson BO, Sorensen SE (1980) Intra-arterial blood pressures at rest and during exercise after surgery for coarctation of the aorta. Eur J Cardiol 11:245–257 14. Helgason H, Eyjo´lfsson K, Alfreðsson H (1988) Coarctation of the aorta in Icelandic children born 1968–1987. In: XXII Nordiska Pediatriska Kongressen, Program och Abstrakt, no. 42, p 39 15. James WF, Kaplan S (1974) Systolic hypertension during submaximal exercise after correction of coarctation of the aorta. Circulation 49/50 (Suppl II):27–34 16. Lerberg DB, Hardisty RL, Siewers RD, et al (1982) Coarctation of the aorta in infants and children: 25 years of experience. Ann Thorac Surg 33:159–169 17. Liberthson RR, Pennington DG, Jacobs ML, et al (1979) Coarctation of the aorta: review of 234 patients and clarification of management problems. Am J Cardiol 43:835–840 18. Malan JE, Benatar A, Levin SE (1991) Long-term follow up of coarctation of the aorta repaired by patch angioplasty. Int J Cardiol 30:23–32 19. Maron BJ, O’Neal Humphries J, Rowe RD, et al (1973) Prognosis of surgically corrected coarctation of the aortae: a 20-year postoperative assessment. Circulation 47:119–126 20. Nanton MA, Olley PM (1976) Residual hypertension after coarctectomy in children. Am J Cardiol 37:769–772 21. Pelech AN, Kartodihardjo W, Balfe JA, et al (1986) Exercise in children before and after coarctectomy: hemodynamic, echocardiographic, and biochemical assessment. Am Heart J 112:1263– 1270 22. Salzer-Muhar U, Kaliman J, Wimmer M, et al (1987) Exercise testing after surgical repair of coarctation of the aorta. Pediatr Cardiol 8:17–22 23. Smith RT, Sade RM, Riopel DA, et al (1984) Stress testing for comparison of synthetic patch aortoplasty with resection and end to end anastomosis for repair of coarctation in childhood. J Am Coll Cardiol 4:765–770 24. Williams WG, Shindo G, Trusler GA, et al (1980) Results of repair of coarctation of the aorta during infancy. J Thorac Cardiovasc Surg 79:603–608
