Although overt myxedema is rare today, however, subclinical hypothyroidism may cause some cardiac manifestations such as diastolic dysfunction(3).
Shiraz E Medical Journal, 7 Vol. 2, No. 1, January 2001
In the name of God
Shiraz E Medical Journal Vol. 2, No. 1, January 2001 http://semj.sums.ac.ir/vol2/jan2001/hypothy&heart.htm
Cardiovascular Manifestations Of Hypothyroidism. Nikoo M H.
Resident, Section of Cardiology, Department of Internal Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
Abstract: At the first look a hypothyroid heart resembles congestive heart failure, however, there are some important clinical and paraclinical differentiating points. Hypothyroidsm has many effects on the cardiovascular system which some of them are pericardial effusion, hypertension, hyperlipidemia, coronary artery disease, congestive heart failure and primary pulmonary hypertension. Congenital hypothyroidsm has the same effects except for rarity of pericardial effusion. Electrocardiographic and echocadiographic effects of hypothyroidsm and also effect of cardiovascular diseases and procedures on the thyroid function are mentioned in the article.
Introduction:
hypothyroid heart. Hypothyroid patients
When you are visiting a patient with a constellation of dyspnea, cardiomegally, pleural effusion, lower extremity edema and ST-T changes on ECG, your impression in most cases is congestive heart failure, but you must remember that hypothyroid heart is very similar to congestive heart failure but with some differen(1)
tiating points.
ume and plasma volume. Circulation time is prolonged, but right and left heart filling pressure are usually within normal limits unless they are elevated by pericardial effusion. There is a redistribution of blood flow with marked reduction in cerebral and renal flow and significant reduction in cutaneous flow.(1) In patients with hypothyroidism the skin microvascu-
In hypothyroid heart in contrast to congestive heart failure, pulmonary pressure is not increased, cardiac output increased properly in response to exercise and Valsalva maneuver is abnormal.(1)
have reduced cardiac output, stroke vol-
Other
differences are normal cathecolamines and normal response to cathecolamine in
lar autoregulatory mechanisms are disturbed
(2)
. A delay in relaxation of skele-
tal muscle is a well- known finding in hypothyroidism; measurements of isovolumetric relaxation time, reveals a prolongation of this interval. In addition there is lengthening of the pre-ejection period and an increased ratio of the pre- ejec-
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Shiraz E Medical Journal, 8 Vol. 2, No. 1, January 2001
tion period to the left ventricular ejection (1)
Hypercholestrolemia
and
hypertriglyc-
eridemia are found in the majority,with
time.
all
cholesterol
subfractions
being
in-
The heart in overt myxedema is often
creased. A direct association between
pale, flabby, and grossly dilated. Classic
hypothyroidism and coronary heart dis-
findings of overt myxedema are : cardiac
ease (CHD) is controversial, since no di-
enlargement, dilatation, significant bra-
rect correlation between cholesterol level,
dycardia, weak arterial pulses, hypoten-
coronary artery disease, and mild hypo-
sion, distant heart sounds, low ECG volt-
thyroidism has been found.(8) Although
age, non-pitting edema and evidence of
CHD is common pathologically, angina
congestive heart failure.(1)
pectoris is present in only seven percent, and the incidence of autopsy proven
Myxedema is associated with increased capillary permeability and
subsequent
leakage of protein into the interstitial space, resulting in pericardial effusion. Rarely, the presenting symptom is complicated by tamponade.(1) Although overt myxedema is rare today, however, subclinical hypothyroidism may cause some cardiac manifestations such as diastolic dysfunction(3) or increased risk of atherosclerosis and myocardial infarction in elderly women.(4) There is an increased frequency of hypertension in patients with hypothyroidism, although not in severe myxedema.(1) Restoration of euthyroidism with thyroxin therapy usually results in a substantial reduction in both systolic and diastolic blood pressure.(5) The individuals with mild to moderate hypothyroidism usually
myocardial infarction is not high in the hypothyroid
population.(8)
Short
term
severe hypothyroidism as encountered in athyroetic patient after cessation of thyroxin for several weeks is not associated with impairment of myocardial perfusion.(9) One study showed that the prevalence of hypothyroidism in patients with primary pulmonary
hypertension (PPH) is high.
Patients with PPH should be investigated for the possibility of co-existing hypothyroidism.(10) Rare associations are found between hypothyroidism and Young Simpson syndrome which manifests with congenital hypothyroidism, facial
dys-
morphism, congenital heart defect and mental retardation(11). Another rare link is found with Down syndrome that includes the association of hypothyroidism with atrial septal defect in this syndrome. (12)
have an increased possibility of developing hypertension, particularly diastolic hypertension, while individuals with severe hypothyroidism are more likely to have normal or slightly low blood pressure.(1) However, in some studies, no association was found between hypertension and hypothyroidism.(6,7)
Cardiovascular manifestation of congenital hypothyroidism are similar to acquired hypothyroidism except for the rarity of pericardial effusion.(1,
13)
Thus the size of
left ventricle, capacity, and posterior thickness are all less in hypothyroid infants. Since heart rate is also lower, cardiac output is reduced. There is also a
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Shiraz E Medical Journal, 9 Vol. 2, No. 1, January 2001
prolongation of the pre-ejection period of the left ventricle.
(1)
children after cardiac surgery that may contribute to post operative cardiac and respiratory
dysfunction
and
may
de-
Electerocardiographic findings in hypothyroidism include:
lay recovery.
1-
Sinus
bradycardia
(usual
)
cantly lower serum levels of thyroid hor-
2-
Sinus
tachycardia
(rare
)
mone, but their subclinical hypothyroid or
prolongation
thyroid autoimmunity did not seem to be
of
wave
related to the development of CHD.(17)
5- Ventricular tachycardia, because of
3- Iodine exposure during cardiac cathe-
bradycardia
hypothermia
terization or surgery of pregnant woman
6- Pericardial effusion findings ( low volt-
may induce transient hypothyroidism in
age
term infants.(18)
34-
QT Decreased
amplitude and
P,
p
QRS,
T)
(16)
2- Female patients with CHD had signifi-
7- Atrioventricular and interventricular block
Other interesting reports are high captur-
8- Incomplete or complete right bundle
ing threshold for pacemaker in a hypo-
branch block (1) 9- Atrial fibrillation
thyroid patient
(14)
(19)
and hypothyroidism as
a cause of lithium induced sinus node Echocardiographic finding in hypothyroidism include:
dysfunction.(20) At last, hypothyroidism
1- Interventricular septal dimensions are
ventricles in dogs. Homogenous prolon-
significantly raised in moderate subclini-
gation of repolarization and refractori-
cal and in severe overt hypothyroidism.
ness may contribute to the antifibrillatory
has a significant antifibrillatory effect on
action of hypothyroidism.(21) 2- Left ventricular posterior wall thickness was significantly increased only in overt hypothyroidism. 3- Right ventricular wall thickness and left ventricular internal dimension have no changes. 4- Pericardial effusion and diastolic dysfunction was seen significant cases only in overt hypothyroidism.(15) Effect of cardiovascular procedures and diseases on the thyroid: An interesting matter is the effects of some cardiac diseases or cardiologic procedures on thyroid function. These include:
Conclusion: Hypothyroidism has numerous effects on the
cardiovascular
system,
increased
capillary permeability leads to pericardial effusion & increased systemic vascular resistance causes hypertension. Due to decrease in heart rate, contractility and total body volume, stroke, volume and cardiac output are diminished.
References: 1. Gordon-H.Williams, Leonard S. Lily, and Elen W.Seely. The heart in endocrine and nutritional disorders. in : Heart disease a textbook of cardiovascular medicine, Braunwald. 5th Ed. W. B. Saunders company. Chap 61, 1997:1885-1913.
1- Transient secondary hypothyroidism in
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Shiraz E Medical Journal,10 Vol. 2, No. 1, January 2001
2.Pazos.Moura.CC; Moura. EG, Breiten bach. MM, Bouskela. E. Nailfold capillarscopy in hypothyroidism and hyperthyroidism : blood flow velocity during rest and post-occlusive reactive hyperemia. Angiology. 1997, 49 :471-6.
3. Brondi. B, Fazio. S, Palmieri. EA, et al. Left ventricular disatolic dysfunction in patients with subclinical hypothyroidism. J clin Endocrinol Metab, 1999 ; 84 :2064-7. 4. Hak.AE, Pols. HA, Visser. TT, et al. Subclinical hypothyroidism is an independent risk factor for atherosclerosis and myocardial infarction in elderly woman: the Rotterdam study. Ann Internal Med, 2000. 132: 270-8. 5. Fletcher. AK, Weetman. AP. Hypertension and hypothyroidism. J Hum Hypertens 1998 ;12:79-82. 6. Bergus.GR, Mold. JW, Barton. ED. et al. The lack of association between hypertension and hypothyroidism in a primary care setting. J Hum Hypertens. 1999 ; 13: 231-5. 7. Bergus. GR, Randall. C, Van. Peursem.R, Lack of association between hypertension and hypothyroidism in post-menopausal women seen in a primary care setting. J AM Board Fam -Pract. 1997 ; 10: 185-91. 8. Zonszein.J. Sonnenblick. EH, Endocrine disease and the cardiovascular system. In : The heart, Alexander.RW, Schlant. RC, Fuster. V. 9th ed.McGraw Hill 1998; PP: 2117-2142. 9. Prasch. F, Wogritsch. S; Hurtl. I, et al. Severe short term hypothyroidism is not associtated with an increased incidence of myocardial ischemia as assessed by thalium 201 stress / rest myocardial scintigraphy. Thyroid 1999; 9: 155-8. 10. Curnock. Al, Dweik. RA, Higgins.BH, et al. High prevalence of hypothyroidism in patients with primary pulmonary hypertension. Am J Med. SCT. 1999; 318: 289-92.
thyroidism in children with Down syndrome in Trabzon, turkey. Turk J pediater, 1998; 40:103-9. 13. Isobe. M, Takahashi. W, Urushibata.K, Sekiguchi. M. Massive pericardial effusion in an adult case of congenital hypothyroidism due to a sublingual thyroid. Acta Cardiol. 1998; 53:101-3. 14. Gerritsen -RJ, van-den-Brom-WE, Stokhot.AA. Relationship between atrial fibrillation and primary hypothyroidism in the dog. Vet.Q 1996; 18: 49-51. 15. Varma. R, Jain. Ak, Ghose.T. Heart in hypothyroidism and echocardiographic study. J Assoc. Physician. India, 1996; 44: 390-2. 16. Betendor F. M, Schmidt. KG, Tiefenbacher.U, et al. Transient secondary hypothyroidism in children after cardiac surgery. Pediatr Rest. 1997; 41: 375-9. 17. Miura. S, Titaka. M, Suzuki. s, et al. Decrease in serum level of thyroid hormone in patients with coronary heart disease. Endocr J 1996; 43 657-63. 18. Linder. N. Sela. B, German.B,et al. Iodine and hypothyroidism in neonates with congenital heart disease Arch Dis Child. fetal. neonatal. Ed, 1997; 77: F239-40. 19. Emilsson. K, Oddsson. H, Allared. M, Brorson.L. An unusual cases of high threshold values at pacemaker implantation. Pacing Clin Electerophysiol. 1997; 366-7. 20. Numata. T, Abe. H, Terao. T, Nakashima.Y. Possible involvement of hypothyroidism as a cause of lithium-induced sinus node dysfunction. Pacing Clin Electorphysiol. 1999; 22:954-7. 21. Liu. P, Fei. L, Wu.W,et al. Effects of hypothyroidism on the vulnerability to ventricular fibrillation in dogs : a comparative study with amiodarone. Cardiovasc Drugs Ther. 1996; 10: 369-78.
11.Masuno. M, Imaizumi. K, Okada. T, et al. Young - simpson syndrome: further delineation of a distinct syndrome. with congenital hypothyroidism. Am. J. Med. Genet, 1999; 84: 8-11. 12. Aynaci. FM, Orhan. F, Celep. F, Karagazel. A. Frequency of cardiovascular and gastrointestinal malformations. Leukemia and hypo-
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