Diagnostic Testing: Difference between revisions

==Electrocardiography (ECG)==

   

An ECG can be used to directly clarify the mechanism of an irregular heart rhythm detected on physical examination or that of an extremely rapid or slow rhythm. In addition the ECG can help in identifying structural heart disease (i.e. cardiac hypertrophy), ischemic heart disease (i.e. myocardial infarction) or other causes of symptoms outside of the heart (i.e. pulmonary embolism). So called Holter monitoring or other continuous-ECG monitoring devices allow assessment of cardiac rate and rhythm on a continuous and ambulatory basis. The most common use of ECG monitoring is the evaluation of symptoms such as syncope, near-syncope, or palpitation for which there is no obvious cause and cardiac rhythm disturbances are suspected.

Another example of the helpful use of the ECG is the characteristic changes on the ECG associated with ventricular or atrial enlargement, which could strengthen the diagnosis of cardiomyopathic or valvular disease based on the physical examination.  

Lastly, evidence of conduction abnormalities may help explain the mechanism of arrhythmias causing symptoms such as palpitations, syncope or angina

#Conclusion

   

===Rhythm===

The sinus node (SA) is located in the roof of the right atrium. It is the fastest physiological pacemaker. When the sinus node generates an electrical impulse, the surrounding cells of the right atrium depolarize. Then the cells of the left atrium, the AV (atrioventricular)node, follow, and at last the ventricles are stimulated via the His bundle. The presence and assessment of P-wave morphology is necessary to determine the rhythm. Normal sinus node rhythm can be presumed if the following criteria are met:

===Conduction===

====PQ interval====

The PQ interval starts at the beginning of the atrial contraction and ends at the beginning of the ventricular contraction.

*Negative (or inverted) T wave

'''Compare the old and the new ECG'''

==Echocardiography==

   

   

The non-invasive echocardiography has now largely replaced cardiac catheterization for calculation of the hemodynamics changes caused by valvular disease. Several examples of methods to examine hemodynamics of the heart and valves by echocardiopgraphy are:

*Cardiac output and pressure gradients can be used to calculate the stenotic valve area.

   

With TEE a smaller ultrasound probe is placed on a gastroscopic device for introduction in the oesophagus behind the heart. Besides overcoming structural problems, in general TEE produces much higher resolution images of posterior cardiac structures. With TEE left atrial thrombi, small mitral valve vegetations, and thoracic aortic dissection can be diagnosed a high degree of accuracy. The downside of the techniques is the invasiveness of the procedure; the introduction of a probe into the oesophagus is very often experienced as rather uncomfortable by patients.

==Cardiac stress test==

Cardiac stress testing is a test used to measure the heart’s ability to respond to external stress in a controlled environment. The stress response of the heart in the test is induced by exercise, such as treadmill walking or biking, or by mimicked by drugs, such as adenosine, dipyridamole or dobutamine. Exercise is the preferred modality for inducing cardiac stress and increasing myocardial oxygen demand. Two main reasons for a pharmalogical induced stress test are; the patient's inability to exercise adequately because of physical or psychologic limitations; or the chosen test does not go along with exercise (i.e., PET scanning). Methods used in stress testing are:

*Electrocardiography

*Myocardial resonance imaging

   

The induced cardiac stress is most widely used to compare the coronary circulation during exercise with the circulation in rest. An imbalance between myocardial oxygen supply and demand due to coronary disease can be revealed as a result of the increased oxygen demand during stress conditions. By this means stress testing can reveal myocardial ischemia during exercise, while no symptoms are present at rest. Furthermore, stress testing can also be used to determine cardiac reserve in patients with valvular and myocardial disease. Deterioration of left ventricular performance during the test suggests a decline in cardiac reserve that could have therapeutic and prognostic implications.