Cardiac Imaging and Stress Testing

Investigation of the heart

• Blood tests- Troponin and CPKMB are enzymes increased after a few hours of heart attack which are detected in the blood
• ECG (electrocardiogram)- The pumping action of the heart is initiated by a coordinated spread of electrical current which is recorded in a graphical manner called ECG. When there is heart attack, the electrical spread is disturbed and this leaves behind a specific pattern in the ECG which is perhaps the first change noted in the event of a heart attack probably even before the onset of chest pain.
  Remember there should be no hesitation to do an ECG even if there is the slightest doubt of a heart attack
• Echocardiography- It is an Ultrasound imaging modality of the heart where one gets to see the structure and function of the heart and the dynamics of blood flow in it. This modality helps to identify valve defects, wall motion abnormalities of heart attack and other structural defects. Another basic investigation to be done as part of routine health check up or in case of any clinical suspicion.



• Treadmill test – This test involves the individual to walk on a treadmill just like in the gym. But his ECG and vitals are constantly monitored for appropriate response. At the end of the test the health of the persons rhythm, adequacy of BP response and whether there is obstruction in the blood vessel (coronary arteries) to the heart muscles can be ascertained with fair amount of accuracy. An invaluable test to identify blocks in blood vessels when ECG and ECHO are normal and there is still suspicion of coronary artery disease
• Stress thallium – This test is an equivalent to Treadmill test (TMT). Those who are not able to walk due to osteoarthritis of knee or lower limb deformities are ideal candidates. Patients heart is subjected stress with pharmacological agent and a radionuclear tracer used to image the heart muscle. If there is a discrepancy at rest and during stress in the image of the heart it represents a critical block in the coronary arteries. The test is safer than TMT and one does not have to worry about harmful radiation like X-rays
• CT- CORONARY ANGIOGRAM (CTCA)/CT scan of the heart – If the kidney functions are normal then an iodine dye is injected through a vein and when they fill the heart, images are taken with a CT scan and reconstructed. Its important that the heart rate is around 60 and atleast a 128 slice CT scan is used. The structure of the whole heart and all its chambers and blood vessels can be visualized. The test is good for identifying coronary artery abnormalities and any structural defects of the heart.
  
  
  It also tells us the amount of plaque burden and calclium deposits in the coronaries. Can be very informative to the CTVS surgeon to plan complex heart surgeries. The test however subjects the individual to X-rays and a small risk of contrast induced kidney injury
• PET SCAN It is a non invasive test to study the blood flow to the muscles of the heart (coronary arteries) and to characterize the viability of the muscles. Test involves imaging the radionuclear activity of the heart muscles with a ‘PET camera” after injection of a radio tracer. We can aquire a wealth of information about the quantity of the block in the coronary arteries and weather angioplasty will really help the patient. The information can also help to assess whether the heart muscle is alive, partially alive or completely dead(scar tissue- in which case plasty is of no use). Inflammation of the heart due to viral infections or other autoimmune causes can also be identified. The test needs experienced operators/cardiac radiologists to perform and interpret the results and should be done in close consultation with your cardiologist.
• SPECT – Similar to PET scan with some difference in the radionuclear tracer used. PET scan has an edge over SPECT in cardiac studies.
• PET-CT – combination of PET and CT scan of the heart to give a summative information
• CARDIAC MRI- The heart is studied with the help of powerful magnetic field, radio waves and computer. It Can be used to study the detailed structure and function of the heart, presence of coronary artery disease, inflammation of heart muscle and its viability. The test does not involve any harmful radiation and very negligible risk due to gadolinium based contrast usage.