|
| |
Cardiac symptoms are common in H patients (50,51). One can distinguish
between chronotropic alterations, which are manifested by sinus tachycardia,
AF, and shortened PR intervals, and inotropic alterations, which reflect
changes in the contractile behaviour of the heart (e.g., increased cardiac
index, stroke volume, and velocity of wall shortening, as well as decreased
ejection period). Patients with H heart disease frequently complain about
symptoms related to chronotropic alterations. They often experience palpitations,
as well as an irregular and vigorous heart beat. In addition, severely
H patients can exhibit signs of congestive heart failure in the absence
of prior cardiac pathology. The frequent occurrence of cardiac manifestations
in H patients can be the result of H itself, underlying heart disease that
decompensates further by H-induced increased demand on the heart, or increased
occurrence of specific cardiac abnormalities. Detailed examinations indicate
that cardiac output in vigorously exercising patients decreases. This change
is not reversible by b-receptor blockade and can only be eliminated by
treating the underlying H. In addition, H patients frequently complain
of dyspnea on exertion even in the absence of cardiac failure (table).
Since H leads to a weakening of skeletal and intercostal muscles, dyspnea
may be more related to a weakness of respiratory muscles rather than to
cardiac abnormalities themselves. In children, congestive heart failure
may occur in severe H, but symptoms completely disappear after normalisation
of thyroid hormone values. These reports give credence to the occurrence
of decreased cardiac pump function in the absence of underlying cardiac
disease. Non-specific changes, such as necrosis of isolated myocytes of
increased size, small areas of fibrosis, an increased number of mitochondria
or round-cell infiltration, can be identified only, on histologic examinations
of hearts obtained from H patients (5).
| Table: |
Cardiovascular features in patients with hyper- and hypothyroidism |
|
|
Physical Examination |
|
Hemodynamic Changes |
|
ECG/X-Ray/Ultrasound |
|
|
| Hyperthyroidism |
|
|
Tachycardia at rest |
|
 Cardiac output |
|
 QT interval |
|
|
Pulse amplitude |
|
Myocardial contractility |
|
PR interval |
|
|
Systolic murmur |
|
Systolic/diastolic function |
|
ST segment elevation |
|
|
Mitral valve prolapse |
|
Systolic blood pressure |
|
Atrial fibrillation |
|
|
1st heart sound |
|
Blood volume |
|
Wolff-Parkinson White Syndrome |
|
|
Possible 3rd heart sound |
|
Venous resistance |
|
Contraction times |
|
|
Ankle swelling |
|
Arterial resistance |
|
Cardiac hypertrophy |
|
|
Unspecific symptoms
(palpitations, shortness of
breast, chest pain) |
|
Diastolic blood pressure |
|
|
|
|
|
Circulation time |
|
|
| |
| Hypothyroidism |
|
|
Bradycardia |
|
Cardiac output |
|
QT interval |
|
|
Weak pulse |
|
Stroke volume |
|
Conduction abnormalities |
|
|
Hypertension |
|
Myocardial contractility |
|
T-wave inversion |
|
|
Faint heart sounds |
|
Blood volume |
|
Atrioventricular block |
|
|
Quiet precordial findings |
|
Diastolic blood pressure |
|
Pericardial/pleural effusions |
|
|
Exercise tolerance |
|
Peripheral vascular resistance |
|
Cardiac tamponade (rare) |
|
|
Dyspnea on exerction |
|
Circulation time |
|
Ascites |
|
|
Congestive heart failure |
|
|
Ankle swelling |
|
|
