I. Myocardial imaging
Myocardial imaging principle: Myocardial cells have selective uptake ability for certain cations, so radioactive drugs are used to label such substances and injected into the myocardium to make myocardial imaging, and the amount of myocardial aggregation of radioactive drugs is positively correlated with the perfused blood flow of the coronary artery in the area, thus reflecting the perfusion of the myocardium.
Clinical applications.
1. Diagnosis of coronary heart disease.
Myocardial imaging has unique diagnostic value for coronary heart disease, especially myocardial ischemia. It can not only visually observe the degree of myocardial ischemia, but also estimate the extent of the lesion. This method has significantly higher diagnostic sensitivity and specificity than ECG for coronary artery disease, and can also detect asymptomatic myocardial ischemia. Its diagnostic sensitivity is 87-93%; specificity: 83-91%. The diagnostic sensitivity for myocardial infarction is even higher (98%).
2. Evaluation of cardiomyocyte viability.
The summation analysis of exercise load and resting image, or nitroglycerin intervention test image can determine the viability of myocardium, especially the identification of hibernating myocardium and infarcted myocardium, which is of great value in deciding whether to reperfuse treatment and its efficacy assessment.
3.Evaluation of treatment efficacy and prognosis of coronary artery disease.
Myocardial imaging of patients with coronary artery disease can be compared before and after coronary artery bypass grafting, PTCA and other treatments to evaluate the therapeutic efficacy; it can also be used for the observation of the effect of thrombolytic therapy for acute infarction, and the prognosis of coronary artery disease can be judged according to the extent of perfusion, redistribution, heart chamber size and heart-lung ratio.
4. Auxiliary diagnosis of cardiomyopathy.
II. Principle of positive myocardial imaging visualization.
Some radioactive drugs are not concentrated in normal myocardium, but can be involved or combined in infarcted or necrotic myocardial lesions to make the infarct lesions visible.
Clinical application: for the diagnosis of acute heart attack
Positive rate: Within one week after the onset of clinical symptoms, the positive rate of penetrating myocardial infarction is 95% and that of subendocardial infarction is about 80%; the positive rate decreases as the onset time increases.
2.Specificity: The specificity is not high and needs to be combined with clinical analysis, such as drug myocardial toxicity, myocarditis, myocardial abscess, myocardial contusion, myocardial calcification and pericarditis, etc. can be revealed.
3.Clinical application value.
In 20-30% of patients with unstable angina with multiple focal myocardial necrosis and cardiomyocyte lysis on histological examination and no elevation of serum enzymes, this method can detect the lesion.
In 25-50% of inferior posterior left ventricular myocardial infarctions, there is often a right ventricular infarction associated with the infarction, and conventional methods are not very helpful in diagnosing the presenting right ventricular infarction, while this method can detect the typical signs.
Cardiac blood pool imaging and cardiac function measurement
1. Principle of imaging.
Using the physiological signal multi-gate circuit technology, the subject’s own ECG R-wave and R-R interval of equal duration is used as the signal to trigger the start? Camera, so as to obtain a series of images of the inner ventricle of a cardiac cycle.
2. Characteristics of nuclear cardiac function and comparison with other methods.
Comparison with catheter method ventriculography: the two have good correlation of EF, PFR and other indexes, but this method is non-invasive, reproducible and easily accepted by patients; the results are not affected by cardiac geometry factors; it can perform exercise test; it can observe local cardiac function changes and improve the diagnosis rate of coronary heart disease.
Comparison with ultrasound cardiography: Both are non-invasive examinations, however, ultrasound examination results are more influenced by ventricular geometry factors and operator’s technique and experience. And it cannot perform electrophysiological analysis and determine the comprehensive local cardiac function to understand the local cardiac function characteristics.
3.Clinical applications.
(1) Diagnosis of myocardial ischemia in coronary heart disease and evaluation of ventricular function
In the resting state, the systolic function of the left ventricle is mostly normal in patients with mild ischemia, and its sensitivity for diagnosing myocardial ischemia is not high, but the determination of cardiac function in the exercise state, combined with phase analysis, has high specificity and sensitivity for coronary heart disease (specificity 90-100%, sensitivity 90-94%), and can make early diagnosis of coronary heart disease and determine the reserve function of the myocardium.
(2) Judgment of cardiac function before and after treatment of heart diseases
Follow-up of patients with acute heart attack before and after treatment: In patients with acute heart attack, both systolic and diastolic functions of the heart are decreased and accompanied by local ventricular wall motion disorders, which are normal, and cardiac function is gradually restored as the condition improves. If the indicators of systolic and diastolic function do not improve or decline during monitoring, it suggests the occurrence of complications or poor prognosis. The recovery of infarct site function can also be observed. Assessment of cardiac function before surgery to determine the patient’s ability to tolerate surgery.
Judgment of the efficacy of new clinical drug treatment and other methods and the study of the mechanism of drug action.
(3) Diagnosis of ventricular wall tumors
Ventricular wall tumor is one of the common complications of acute and old infarction, with an incidence of 15-20%. Nuclear cardiac function testing can be performed by observing ventricular wall motion, with limited amplitude drop and phase changes seen in phase analysis. The diagnostic compliance rate is as high as 95%. If X-ray ventriculography is used as the standard, the sensitivity and specificity of the method are 100%.
(4) Evaluation of cardiac function in chronic obstructive pulmonary disease
Right ventricular dysfunction is its common complication. RVEF, which represents right ventricular systolic function, is closely related to right ventricular afterload and negatively correlated with pulmonary artery pressure, and changes in RVEF to varying degrees in the early stage of pulmonary heart disease.
(5) Observation of cardiac conduction process and diagnosis of conduction abnormalities
Time-phase analysis can visualize the starting point and pathway of myocardial excitation conduction. It can be used to show the abnormal channels and abnormal excitation foci in preexcitation syndrome and 3 ventricular rhythm abnormalities; it is the preferred method to observe the efficacy of bypass resection and radiofrequency ablation; it can also detect the site of impulse generation and conduction pattern of pacemaker, and observe the efficacy of pacemaker therapy.
It can also detect the site of pacemaker impulse generation and conduction pattern, and observe the efficacy of pacemaker therapy.
Nuclear cardiovascular angiography
It can be used for the diagnosis of congenital heart disease and large vessel malformation, etc. This method has complementary effects and mutual verification with ultrasound and cardiac catheterization. This method has the advantages of non-invasive, reproducible, quantitative analysis and dynamic observation.