Guías de actuación clínica de la Sociedad Española de Cardiología. Cardiología nuclear: bases técnicas y aplicaciones clínicas

Imaging techniques and the evaluation of the right heart and the pulmonary circulation

Since the right side of the heart and the pulmonary circulation are regarded as secondary components of the circulatory system, their role in disease has traditionally not received the same attention as their counterparts in the systemic circulation. This was partly because precise noninvasive study of these structures was difficult. For many years, chest radiography and invasive angiography were the only techniques available for imaging the minor circulation. The development of transthoracic echocardiography and nuclear techniques has produced a significant leap forward for noninvasive imaging, particularly of the right ventricle. More recently, novel echocardiographic techniques, and advances in computed tomography and magnetic resonance imaging, in particular, have expanded our diagnostic armamentarium and provided new insights into the anatomy and function of the pulmonary circulation in both health and disease. This article contains a review of the current status of techniques for imaging the right side of the heart and the pulmonary circulation.

[Risk stratification after acute myocardial infarction]

In recent years, the characteristics of patients who suffer acute myocardial infarction without complications during hospitalization have changed. In addition, the range of non-invasive studies available for evaluating left ventricular systolic function, residual myocardial ischemia, and myocardial viability in these patients has improved. Left ventricular systolic function and residual ischemia should be evaluated in all patients before release. The non-invasive technique used (exercise test, echocardiography, nuclear cardiology, magnetic resonance imaging) depends on availability, experience, and results at each institution. Coronary arteriography should be performed in patients with significant ischemia or severe left ventricular systolic dysfunction in non-invasive studies. In these cases coronary angiography must be performed to determine if coronary arteries are suitable for revascularization before performing a test of myocardial viability.

[Exercise-induced left bundle-branch block in patients with coronary artery disease versus patients with normal coronary arteries]

INTRODUCTION AND OBJECTIVES

Exercise-induced left bundle-branch block does not always denote the presence of underlying coronary artery disease. The aim of this study was to analyze the clinical characteristics and evolution of patients with rate-dependent left bundle-branch block.

PATIENTS AND METHOD

9,318 consecutive exercise stress studies were reviewed. The clinical characteristics and evolution (mean follow-up: 6.9 years) of 20 patients with exercise-induced left bundle-branch block in which coronary angiography had been performed were analyzed.

RESULTS

Eight out of 20 patients had normal coronary arteries (group A) and 12 had coronary artery disease (group B). Peak O2 consumption, peak myocardial O2 consumption, and heart rate when block appeared (132 20 vs. 95.4 23 beats/min; p = 0.002) were significantly higher in group A. Seven of the 8 patients with normal coronary arteries had chest pain coinciding with the first beat of left bundle-branch block. There were no deaths during follow-up in group A, but permanent left bundle-branch block appeared in 5 patients of this group who experienced disappearance of exercise-related pain. There were 3 deaths in group B and 2 patients had acute myocardial infarction during follow-up. One patient in each group developed atrioventricular block and required pacemaker implantation.

CONCLUSIONS

In contrast with patients with left bundle-branch block and coronary artery disease, the prognosis of patients with painful left bundle-branch block and normal coronary arteries is good. However, the development of permanent left bundle-branch block is frequent. Atrioventricular block, although rare, may occur.

[Prognostic value of normal myocardial radionuclide scan in patients with positive treadmill test]

The purpose of this study was to determine the prognostic value of a normal 201Tl scan in patients with a positive treadmill exercise stress test. We analyzed retrospectively 85 consecutive patients with a positive treadmill exercise test and normal Tl201 scan who were studied for the diagnosis of coronary artery disease from January 1996 to December 2000. The pretest probability of coronary artery disease was intermediate or high in all patients. Seventy-eight patients (89%) were followed up for 2.03 years. Forty patients (51%) were men. Age was 56 years. The cardiac events considered were angina, revascularization, nonfatal myocardial infarction, and cardiac death. During the follow-up period, none of the patients suffered a major cardiac event. Eight patients had episodes of chest pain and one had angor that required revascularization. Patients with an intermediate probability of coronary artery disease before the test and normal myocardial radionuclide scan had a very good prognosis even with a positive treadmill exercise test.

[Chest pain units. Organization and protocol for the diagnosis of acute coronary syndromes]

The two main goals of chest pain units are the early, accurate diagnosis of acute coronary syndromes and the rapid, efficient recognition of low-risk patients who do not need hospital admission. Many clinical, practical, and economic reasons support the establishment of such units. Patients with chest pain account for a substantial proportion of emergency room turnover and their care is still far from optimal: 8% of patients sent home are later diagnosed of acute coronary syndrome and 60% of admissions for chest pain eventually prove to have been unnecessary.We present a systematic approach to create and manage a chest pain unit employing specialists headed by a cardiologist. The unit may be functional or located in a separate area of the emergency room. Initial triage is based on the clinical characteristics, the ECG and biomarkers of myocardial infarct. Risk stratification in the second phase selects patients to be admitted to the chest pain unit for 6-12 h. Finally, we propose treadmill testing before discharge to rule out the presence of acute myocardial ischemia or damage in patients with negative biomarkers and non-diagnostic serial ECGs.

[Myocardial SPET in hypertrophic cardiomyopathy]

INTRODUCTION AND OBJECTIVES

The aim of this study was to evaluate the diagnostic accuracy of myocardial SPET in patients with hypertrophic cardiomyopathy (HC).

PATIENTS AND METHODS

One hundred and six consecutive patients (aged 53 +/- 12 years, 50 women, 66 with dynamic obstruction) with an echocardiographic diagnosis of HC were studied with exercise-rest myocardial SPET with 99mTc-tetrofosmin. Forty-six (43%) of these patients had chest pain and in 31 (29%) a coronary angiography was performed. Fifty-six per cent of the patients were treated with beta-blockers and 23% with verapamil.

RESULTS

Angina during the exercise test was observed in only 8% of the patients. Perfusion defects were observed in 35% of the patients. Only 8 (26%) out of the 31 patients with angiography had coronary artery disease (stenosis > 50%). When fixed and reversible defects were considered as positive, the sensitivity was 50%, the specificity was 65%, the positive predictive value was 33% and the negative predictive value was 79%.

CONCLUSIONS

Myocardial perfusion defects can be observed in more than one third of medically treated patients with HC. Only a quarter of catheterized patients, even with chest pain, have associated coronary artery disease. The accuracy of SPET for the diagnosis of coronary artery disease in hypertrophic cardiomyopathy is low. Thus, the value of this technique is limited in these patients.