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Biomedical subjects

E Picano

Publications and source records attributed to E Picano.

At least 109 records · Page 6Linked to original sources
PubMed1995

Residual coronary reserve identifies segmental viability in patients with wall motion abnormalities.

OBJECTIVES: The aim of this study was to determine whether the presence of residual coronary reserve can in itself identify viable segments. BACKGROUND: Experimental data suggest that despite hypoperfusion at rest, viable myocardium may exhibit persistence of coronary reserve. Preliminary observations in patients show that in basally dyssynergic areas, a residual vasodilator capability is present despite hypoperfusion at rest and that a flow-mediated increase in regional wall motion identifies residual viability. METHODS: Fourteen patients with evidence of previous myocardial infarction, infarct-related single-vessel coronary artery disease and impaired regional ventricular function at rest underwent positron emission viability imaging by fluorine-18 deoxyglucose. In addition, blood flow at rest and vasodilator capability were regionally evaluated in all patients by means of nitrogen-13 ammonia. RESULTS: Of a total of 252 segments, 133 were dyssynergic at rest. Of these 133 segments, 60 (group 1) showed normal metabolic activity and only mild reduction in myocardial blood flow. The other 73 segments showed a marked reduction in flow; of these, 25 (group 2, viable) had persistent metabolic activity, whereas 48 (group 3, necrotic) did not. Despite similar levels of hypoperfusion at rest, group 2 segments showed a preserved coronary reserve that was virtually absent in necrotic segments (2.6 +/- 1.3 vs. 1.3 +/- 0.5, p < 0.01). This value was similar to that observed in viable group 1 segments (2.5 +/- 1.6, p = NS). CONCLUSIONS: In addition to characterizing myocardium at risk, imaging of coronary flow at baseline and after dipyridamole by positron emission tomography provides helpful information on myocardial viability that may integrate the "static" viability information obtained with the baseline flow/metabolic approach.

Aged↗
PubMed1995

The multicentre trial philosophy in stress echocardiography: lessons learned from the EPIC study. EPIC-EDIC Study Project. Echo Persantine International Cooperative Study. Echo-Dobutamine International Cooperative Study.

The scientific assessment of diagnostic tests should not be based upon a small series of results published by the best academic institutions, but ought to require large scale, multicentre validation founded on grass roots institutions with real doctors, real patients and real problems. To this purpose, an international network of stress echo laboratories has been organized, and within a few years has collected data from thousands of studies using pharmacological stress echocardiography, performed with either dipyridamole (EPIC: Echo Persantine International Cooperative Study) or dobutamine (EDIC: Echo Dobutamine International Cooperative Study) stresses. In a widely deregulated field, all network laboratories have agreed: to pass a quality control examination on stress echo reading before entering the study; to adopt an identical drug infusion protocol; to code similarly the LV segments; and to adopt a common scoring system for wall motion analysis. A minimum amount of historical, clinical, and-when available-stress electrocardiographic, angiographic and follow-up data have been collected on each patient, and disseminated in the various centres, facilitating the creation of an international stress echo language that will help, not only the production of high quality scientific data, but also the build up of a common stress echo lab, with a standardized way of making the studies, unifying the methods and terminology, and archiving data. To date, we have 50 echo laboratories from 15 nations across four continents (Europe, America, Asia and Africa) actively involved in this project. These data will ultimately fill the gap between the academic theory of journals and the pragmatic experience of daily life in a busy echocardiographic laboratory.

Echocardiography↗
PubMed1995

Dipyridamole and dobutamine: competitors or allies in pharmacological stress echocardiography?

Stress echocardiography has become an accepted and cost-effective method for diagnosing coronary artery disease. However, as exercise stress echocardiography is a demanding technique, difficult to reproduce, pharmacological stress echocardiography has become very popular in recent years. The two most popular tests from the pharmacological stress echocardiography arena are dipyridamole and dobutamine. They have enabled the technical limitations inherent in exercise echocardiography to be overcome, and have provided the opportunity to obtain, during stress, images of unchanged quality in comparison to baseline. However, the sensitivity of both pharmacological stresses applied separately is less than ideal in patients with milder forms of coronary artery disease and in patients under therapy. To overcome this, a new generation of pharmacological stress tests, the combined dipyridamole-dobutamine tests were introduced. A combined dipyridamole-dobutamine echocardiography stress test should suggest that the agents are natural allies rather than competitors but in some instances they are applicable only in selected patients, and each pharmacological agent may be clinically contraindicated for administration. This is the message from a large scale study of recent years.

Cardiotonic Agents↗
PubMed1995

Heterogeneity of left ventricular regional wall thickening following dobutamine infusion in normal human subjects.

BACKGROUND: Pathophysiological data and pragmatic clinical experience with stress echocardiography suggest that inotropic stimulation with simultaneous changes in heart rate and loading conditions can affect the function of various myocardial regions asymmetrically, inducing heterogeneity in wall motion and thickening, possibly mimicking 'ischaemic' regional hypokinesis or lack of hyperkinesis during stress. OBJECTIVES: To describe, in a quantitative fashion, the physiological contractile response of different left ventricular regions following dobutamine infusion. METHODS: Two hundred and twenty-three in-hospital patients undergoing dobutamine stress echocardiography and coronary angiography were initially considered. Of these 223 patients, 18 had angiographically normal coronary arteries, normal resting function, negative ergonovine and exercise stress tests, and negative dobutamine stress echocardiograms; of the 18, only in 11 patients (six females, age = 56 +/- 10 years) was it possible to obtain quantitative measurements of the middle segments of the inferior, anterior, lateral, and septal walls. Two-dimensional echocardiographic measurements of wall thickness were obtained at the end-diastolic (onset of Q wave) and end-systolic phases, both at baseline (rest) and at the peak of the dobutamine infusion (40 micrograms.min-1.kg-1 plus atropine). RESULTS: Dobutamine increased heart rate (rest = 69 +/- 9 vs dobutamine = 138 +/- 13 beats.min-1; P < 0.01), whereas systolic blood pressure did not change significantly (rest = 136 +/- 15 vs dobutamine = 150 +/- 25 mmHg, P = ns). During stress, % systolic thickening decreased in the inferior wall (rest = 73 +/- 24 vs dobutamine +/- 50 +/- 9%; P < 0.01), whereas it tended to increase to a variable extent in the other regions, i.e. septal (rest = 46 +/- 17 vs dobutamine = 68 +/- 13%, P < 0.01), anterior (rest 62 +/- 19 vs dobutamine = 69 +/- 11%, P = ns), and lateral wall (rest = 48 +/- 16 vs dobutamine = 61 +/- 18%, P = ns). The decrease in % systolic thickening of the inferior wall was inversely correlated with the increase in end-diastolic wall thickness (r = -0.75; P < 0.01), but neither with heart rate (r = 0.15; P = ns) nor with systolic blood pressure changes (r = 0.05; P = ns). CONCLUSIONS: Heterogeneity of left ventricular wall thickening can be induced or magnified by dobutamine infusion even in subjects without coronary artery disease, with the inferior wall showing a lack of hyperkinesis, up to relative hypokinesis, in comparison with other myocardial regions. Caution in aggressive dobutamine stress echocardiography reading, especially in the inferior wall, might be warranted.

Adult↗
PubMed1995

The value of dipyridamole echocardiography in risk stratification before vascular surgery. A multicenter study. The EPIC (Echo Persantine International Study) Group--Subproject: Risk Stratification Before Major Vascular Surgery.

PURPOSE: Patients undergoing major vascular surgery are at relatively high risk of cardiac events, and pharmacological stress echocardiography is increasingly used for peri-operative risk stratification. PATIENTS AND METHODS: One hundred and twenty-one patients undergoing vascular surgery (age 65 +/- 7 years) were studied by dipyridamole echocardiography testing in six different centres. Of the total 136 patients, 15 were subsequently excluded because surgery was either cancelled (n = 8) or postponed pending cardiac revascularization (n = 7) because of the presence of a 'high-risk' stress echo response (identified 'a priori' as a positive dipyridamole echocardiography testing with a dipyridamole-time < 5 min and/or a peak wall motion score index > 2, upon scoring each segment from 1 = normal to 4 = dyskinetic in an 11-segment model). RESULTS: No major complications occurred during dipyridamole echocardiography testing. Technically adequate images were obtained in all patients; however, in one patient only the low dipyridamole dose (56 mg.kg-1 over 4 min) was given to limit side effects. Of the 121 patients undergoing surgery 28 (23%) had a positive test. Peri-operative events occurred in nine patients (8%): two deaths, two myocardial infarctions, five cases of unstable angina. Sensitivity and specificity of dipyridamole echocardiography testing for predicting cardiac events were 78% and 81%, respectively, with a positive predictive value of 25% and a negative predictive value of 98%. Dipyridamole echocardiography testing effectively singled out patients with, from those without, events, but neither clinical parameters, such as Detsky score, nor baseline echo parameters, such as resting wall motion score index or ejection fraction were able to distinguish between such patients. CONCLUSION: In conclusion, dipyridamole echocardiography testing is safe and well tolerated in patients undergoing major vascular surgery, and provides an effective pre-operative screening test for risk stratification of these patients mainly due to the extremely high negative predictive value. Stress echocardiography is a better discriminator than clinical and rest echocardiographic variables.

Aged↗
PubMed1995

In vivo ultrasonic parametric imaging of carotid atherosclerotic plaque by videodensitometric technique.

Extensive experimental and clinical data show that the ultrasonic image conveys information on the biochemical composition of the atherosclerotic plaque, ie, the relative content of lipids (hypoechoic), fibrous tissue (hyperechoic), and calcific deposits (very echogenic with shadowing). A more dishomogeneous echo structure of the plaque is also more often associated with clinically complicated carotid plaques. To date, however, the assessment of plaque density and homogeneity by transcutaneous B-mode imaging remains subjective and qualitative. The aim of this study was to assess whether plaque echodensity and homogeneity might be established on a more objective and quantitative basis by description of the spatial distribution of echo amplitude (referred to as tissue texture) applied to digitized images, obtained with commercially available B-mode transcutaneous imaging systems. A total of 47 B-mode images derived from echotomographic studies in 10 patients were digitized off line. For each region of interest, a set of first-order (mean gray level, standard deviation, skewness, kurtosis: mathematical descriptors of the shape of the frequency distribution of gray-level histogram) and of second-order (entropy, angular moment: mathematical descriptors of the spatial distribution of gray levels within the region of interest) textural parameters were evaluated. The visual, concordant reading by two independent, experienced observers assigned the plaques on the basis of qualitatively assessed echodensity to three groups: "soft" (n = 18), "fibrotic" (n = 20), "calcific" (n = 9). Regarding spatial gray-level distribution, 46 plaques would be separated into "homogenous" (n = 17) and "dishomogeneous" (n = 29). On digitized images, the normalized mean gray level was the most effective first-order textural parameter for distinguishing soft (24.2 +/- 12.4 arbitrary units in a zero to 255 scale) from fibrotic (64.5 +/- 16.4) and calcific plaques (125.3 +/- 24.5), P < 0.01 for all intergroup differences. "Homogeneous" plaques were separated from "heterogeneous" ones on the basis of entropy (5 +/- 1 vs 7.9 +/- 9.7; P < 0.01), whereas the values of angular second moment overlapped (1.542E-3 + 1.334E-3 vs 5.181E-4 +/- 2.5615E-4, P = ns). In conclusion, quantitative texture analysis of ultrasonic images derived from transcutaneous, high-resolution, commercially available B-scan systems is feasible in man and provides a quantitative operator-independent assessment of plaque echodensity and homogeneity.

Arteriosclerosis↗
PubMed1994

Safety and tolerability of dobutamine-atropine stress echocardiography: a prospective, multicentre study. Echo Dobutamine International Cooperative Study Group.

Diagnostic tests that are hazardous or infeasible, or both, may become accepted before inadequacies are recognised; only multicentre trials can provide the necessary information for an unrestricted acceptance of any new diagnostic procedure. We prospectively studied the results obtained in 24 experienced echocardiography laboratories. 2949 tests were done in 2799 patients. In 341 tests (12% of the overall population, 21% of the negative tests) the test could not be completed because of complex ventricular tachyarrhythmias (134, 38% of all submaximal studies); nausea and/or headache (71, 20%); hypotension and/or bradycardia (62, 17%); supraventricular tachyarrhythmias (44, 12%); hypertension (24, 7%); and others (20, 6%). Dangerous events (life-threatening complications or side-effects requiring specific treatment and lasting more than 3 hours, or new hospital admission) occurred in 14 cases (1 every 210 tests)--9 cardiac (3 ventricular tachycardias; 2 ventricular fibrillations; 2 myocardial infarctions; 1 prolonged antidote-resistant myocardial ischaemia; 1 severe, persistent hypotension) and 5 extracardiac (atropine poisoning with hallucinations lasting several hours in the absence of either myocardial ischaemia or hypotension). Life-threatening and/or longlasting complications may occur during dobutamine/atropine stress echocardiography. The test is generally well tolerated, although may be interrupted by minor, self-limiting, usually symptomless side-effects.

Atropine↗
PubMed1994

Dipyridamole stress echocardiography in patients with severe left main coronary artery narrowing. Echo Persantine International Cooperative (EPIC) Study Group--Subproject "Left Main Detection".

From a population of 2,698 patients (579 evaluated early after an uncomplicated acute myocardial infarction) who underwent dipyridamole echocardiography testing (DET) and subsequent coronary angiography, left main (LM) stenosis > or = 50% was present in 73 (61 men and 12 women, mean age 62 +/- 8 years). These 73 patients were compared with a control group comprising 100 consecutive coronary patients without LM disease. Both groups were similar regarding mean age, sex, incidence of previous myocardial infarction, left ventricular function at rest, and severity of coronary artery disease by the number of diseased vessels excluding the LM. The proportion of patients receiving antianginal therapy during DET was higher in the LM than in the non-LM group (32 vs 14%; p < 0.01). No major complication (severe hypotension, sustained arrhythmia, myocardial infarction or death) occurred during DET. Of 73 patients with LM disease, 68 had positive DET (sensitivity 93%), dipyridamole time was 7.1 +/- 3.8 minutes, and the rest-peak stress variation in dipyridamole wall motion score index (1 = normal to 4 = dyskinesia, in an 11-segment model) was 0.37 +/- 0.23; 14 patients (19%) were resistant to aminophylline and needed nitrates to resolve ischemia. In the non-LM group, DET was positive in 72% (p < 0.001 vs LM), with a longer dipyridamole time (9.6 +/- 5.2 minutes; p < 0.001 vs LM), lower rest-peak stress wall motion score index variation (0.29 +/- 0.25; p < 0.05 vs LM), and less frequent antidote resistance (1%; p < 0.001 vs LM).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Dipyridamole-dobutamine echocardiography: a novel test for the detection of milder forms of coronary artery disease.

OBJECTIVES: This study was designed to assess the clinical, hemodynamic and diagnostic effects of the addition of dobutamine to dipyridamole echocardiography. BACKGROUND: Pharmacologic stress echocardiography with either dipyridamole or dobutamine has gained acceptance because of its safety, feasibility, diagnostic accuracy and prognostic power. The main limitation of the two tests is a less than ideal sensitivity in some patient subsets, such as those with limited coronary artery disease. We hypothesized that two pharmacologic stresses might act synergistically in the induction of ischemia by combining the mechanisms of inappropriate coronary vasodilation (with dipyridamole) and an increase in myocardial oxygen consumption (with dobutamine). METHODS: One hundred fifty patients (mean [+/- SD] age 51 +/- 11 years) referred for stress echocardiography were initially studied by dipyridamole-dobutamine echocardiography. The test was stopped during the dipyridamole step in 95 patients for achievement of a predetermined end point (obvious dyssynergy induced by lower or higher dipyridamole dose), and dipyridamole-dobutamine tests were performed in 55 patients (negative dipyridamole echocardiographic test). In the same 150 patients the dobutamine echocardiographic test (up to 40 micrograms/kg body weight per min) was performed on a separate day. RESULTS: Significant coronary artery disease (> 50% diameter stenosis of at least one major coronary vessel by quantitative coronary arteriography) was present in 131 patients (one vessel in 115; two vessels in 10, three vessels in 6), with normal coronary arteriography in 19. The feasibility of the dipyridamole-dobutamine test was 96%. Self-limiting side effects occurred in 5% of patients. The peak rate-pressure product was lowest during the dipyridamole test (132 +/- 30) and was comparable during the dobutamine (186 +/- 59) and dipyridamole-dobutamine tests (179 +/- 45, p = NS vs. dobutamine; p < 0.01 vs. dipyridamole). Sensitivity was 71% for dipyridamole, 75% for dobutamine and 92% for dipyridamole-dobutamine echocardiography (dipyridamole vs. dipyridamole-dobutamine, p < 0.01; dobutamine vs. dipyridamole-dobutamine, p < 0.01; dipyridamole vs. dobutamine, p = NS), whereas specificity was 89% for dipyridamole, 79% for dobutamine and 89% for dipyridamole-dobutamine echocardiography (p = NS for all). CONCLUSIONS: Routine dobutamine addition to dipyridamole stress testing is clinically useful and well tolerated. It expands the spectrum of the disease detectable by pharmacologic stress echocardiography and allows documentation of milder forms of coronary artery disease that can be missed by conventional dipyridamole or dobutamine stress echocardiography.

Adult↗
PubMed1994

Short-term cardiac adaptation to severe haemodilution: an echocardiographic study in normal and hypertensive subjects.

In order to avoid transfusion risks and optimize blood bank resources, in recent years many blood sparing techniques have been proposed, including severe haemodilution. The aim of this study is to assess the pattern of normal haemodynamic and cardiac adaptation to severe haemodilution in patients undergoing major orthopaedic surgery and refusing blood transfusions for religious reasons (the patients were Jehovah's Witnesses). Two-dimensionally guided M-mode echocardiograms were performed at baseline and 4 days after major orthopaedic surgery in 26 Jehovah's Witnesses (age 61 +/- 11 years), with normal regional and global baseline left ventricular function and no valvular disease. Left ventricular (LV) volumes were estimated by using the Teichholz formula. From the latter, we calculated ejection fraction and stroke volume, cardiac output (stroke volume x heart rate), and total peripheral resistance estimated as mean arterial pressure by cuff sphygmomanometer x 80/cardiac output. On the basis of LV mass (ASE-cube corrected by Devereux), two groups were identified: non-hypertrophic (LV mass index < 110 g.m-2 in women and < 130 g.m-2 in males) and hypertrophic. In the 19 patients without LV hypertrophy, haemoglobin decreased from 13.5 +/- 1.6 (mean +/- standard deviation) g.dl-1 (at baseline) to 8.7 +/- 1.3 post-operation (P < 0.01), and peripheral vascular resistances fell from 2131 +/- 450 to 1278 +/- 310 (dyne.s.cm-5) (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Christianity↗
PubMed1994

Assessment of anatomic and physiological severity of single-vessel coronary artery lesions by dipyridamole echocardiography. Comparison with positron emission tomography and quantitative arteriography.

BACKGROUND: The aim of this study was to compare the results of dipyridamole-echocardiography test (DET: two-dimensional echo monitoring during dipyridamole infusion up to 0.84 mg/kg over a period of 10 minutes) with both anatomic and physiological parameters of coronary artery disease severity, assessed by computer-assisted quantitative coronary arteriography, and regional coronary flow reserve, measured by [13N]ammonia (13NH3) and dynamic positron emission tomography (PET), respectively. METHODS AND RESULTS: We studied 31 patients with a history of chest pain and neither previous myocardial infarction nor resting wall motion abnormalities. Eighteen patients had single-vessel disease (> 50% stenosis of one major coronary vessel), and 13 had normal coronary arteries. The criterion for DET positivity was the appearance of a new transient regional wall motion abnormality. In patients with a positive DET, two parameters were evaluated: the dipyridamole time (ie, the time from the beginning of drug infusion to the development of obvious dyssynergy) and the wall motion score index (WMSI, a semiquantitative integrated estimation of extent and severity of the stress-induced dyssynergy). WMSI was derived by summation of individual segment scores divided by the number of segments interpreted. Quantification of regional myocardial blood flow was obtained by PET measurements of 13NH3 arterial input function and left ventricular myocardial tissue concentration both at control and after dipyridamole (0.56 mg/kg over 4 minutes). Maximal regional blood flow after dipyridamole in the region supplied by the stenotic vessel was significantly lower in the 11 patients with coronary artery disease and positive DET than in the 7 patients with coronary artery disease and negative DET (1.08 +/- 0.33 versus 1.98 +/- 0.37 mL.min-1.g-1, P < .01). In patients with a positive DET, regional coronary flow reserve correlated well with dipyridamole time (r = .87, P < .01) but not with peak WMSI (r = .25, P = NS). Patients with dipyridamole-induced akinesia or dyskinesia (n = 6) had a greater reduction in regional coronary flow reserve than did those showing hypokinesia (n = 5): 1.38 +/- 0.51 versus 2.17 +/- 0.42, P < .05. Percent area reduction was more severe in patients with DET positivity than in those with DET negativity (93.7 +/- 8.7% versus 77 +/- 10.3%, P < .01), and it correlated with regional coronary flow reserve (r = .64, P < .01) and dipyridamole time (r = -.59, P < .01). CONCLUSIONS: In patients with single-vessel disease, DET shows an excellent specificity but a limited sensitivity; in these patients, DET positivity is associated with a physiologically important coronary stenosis. Severity of the anatomic stenosis and impairment in regional flow reserve are greater when the dipyridamole-induced dyssynergy appears earlier during the test. Therefore, a stratification of the anatomo-physiological severity of coronary artery disease can be obtained with DET, based mainly on the temporal allocation of the transient dyssynergy.

Adult↗
PubMed1994

Diagnostic and prognostic value of dipyridamole echocardiography in patients with suspected coronary artery disease. Comparison with exercise electrocardiography.

BACKGROUND: Before any new diagnostic test is accepted in clinical practice, such a test should be compared with established diagnostic tools in an appropriately large series of patients encompassing the complete spectrum of challenges to which the test is exposed. The aim of the present study was to assess the relative diagnostic and prognostic accuracies of high-dose dipyridamole echocardiography (two-dimensional echocardiographic monitoring during dipyridamole infusion up to 0.84 mg/kg over 10 hours) versus maximal symptom-limited bicycle exercise ECG test in patients with angina. METHODS AND RESULTS: We studied 429 consecutive in-hospital patients who met the following inclusion criteria: history of chest pain, off antianginal therapy for at least 2 days (1 week for beta-blockers), no previous myocardial infarction and/or obvious regional left ventricular dyssynergy of contraction (akinesis or dyskinesis) at baseline, and acceptable acoustic window under resting conditions. All patients underwent dipyridamole echocardiography and exercise ECG--on different days and in random order--within 1 week of coronary angiography (which was performed independent of test results) and were followed up for 37.8 +/- 14 months (range, 1 to 73 months). Criteria of positivity were for dipyridamole echocardiography, a transient regional dyssynergy absent in the baseline examination; for exercise ECG, an ST-segment shift of > or = 0.1 mV from baseline; and for coronary angiography, a luminal reduction of > or = 75% in at least one major coronary vessel (50% for left main). There were 183 patients without and 246 with coronary artery disease; 132 had one-, 70 had two-, and 44 had three- and/or left main vessel disease. The specificity was higher for dipyridamole echocardiography than for exercise ECG (90% versus 51%, P < .001). The overall sensitivity of dipyridamole echocardiography was similar to that of exercise ECG (75% versus 74%, P = NS), with no significant differences in the subset with one- (67% versus 69%, P = NS), two- (79% versus 77%, P = NS), or three- (93% versus 86%, P = NS) vessel disease. During the follow-up, there were 20 deaths, 13 nonfatal myocardial infarctions, and 126 revascularization procedures. In the univariate analysis, dipyridamole resulted in higher chi 2 values than did exercise stress testing. A Cox forward stepwise survival analysis identified the dipyridamole time as the most powerful prognostic predictor of death (chi 2 = 19.4, P < .0001) of all invasive and noninvasive parameters. The dipyridamole time also provided independent and additional prognostic information when it was adjusted for age, diabetes, resting ECG, and exercise stress test according to a modified, interactive stepwise procedure. This is true when death only, death and myocardial infarction, and death, myocardial infarction, and revascularization procedures were considered end points. CONCLUSIONS: In patients with no previous myocardial infarction and good resting left ventricular function, compared with exercise ECG, dipyridamole echocardiography has a similar sensitivity and a higher specificity for the noninvasive detection of angiographically assessed coronary artery disease. Dipyridamole echocardiography also provides information in addition to that provided by exercise ECG for predicting death, infarction, and all events when the presence as well as the timing, severity, and extension of dipyridamole-induced wall motion abnormalities are considered.

Coronary Angiography↗
PubMed1994

Detection of viable myocardium by dobutamine and dipyridamole stress echocardiography.

The basic aspect of cell behaviour that is the clue for viability recognition by stress echo is regional function. By definition, the function is depressed both in viable and in necrotic segments. However, only viable segments retain a contractile reserve; which can be evoked by an inotropic challenge, either cathecolaminic or flow-mediated, as consistently shown by several experimental studies. This is the basis of viability recognition by pharmacological stress echocardiography. Both dobutamine and dipyridamole exploit the same pathophysiological principle: viable tissue has a residual contractile reserve, which can be elicited by an appropriate inotropic stimulus. With dobutamine, the stimulus is a beta-receptor mediated effect on myocardial cell, which is later matched by an increase in flow. With dipyridamole, the primary stimulus is an adenosine A2-receptor mediated effect on the coronary arteriole smooth muscle cell, leading to an increase in flow. At that point, the increase in function is to be expected on the basis of the known relationship between myocardial contractility and coronary perfusion. From the technical point of view, the "viability window" is dose-related with dobutamine, and time-related with dipyridamole--where the same dose is associated to an early inotropic phase followed by a later ischemic response. In spite of the different pathophysiological background and technical modalities, dobutamine and and dipyridamole have shown a similar sensitivity and specificity for prediction of viability, with an overall accuracy only marginally lower than resting thallium. The practical, clinical impact of these observations is still blunted by relatively small numbers of observations in highly selected populations including a limited number of patients and studies in very few centers.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Circulation↗
PubMed1994

Regression of hypertensive myocardial hypertrophy does not affect ultrasonic myocardial reflectivity: a tissue characterization study.

OBJECTIVE: Ultrasonic backscatter from the myocardial walls is directly related to the morphometrically or biochemically evaluated collagen content in man, and shows a normal pattern of quantitatively assessed ultrasonic backscatter in hypertensive patients, even in the presence of left ventricular hypertrophy. Whether the pharmacologically induced regression of left ventricular hypertrophy in hypertensive patients is accompanied by a disproportionate increase in relative connective tissue content is not yet known. The objective of the present study was to assess the effects of regression of left ventricular hypertrophy on the quantitatively evaluated myocardial reflectivity in essential hypertensives. DESIGN: We evaluated 19 mild-to-moderate essential hypertensives with echocardiographically assessed left ventricular hypertrophy, before and after 8 months' effective antihypertensive therapy with 20-40 mg enalapril once a day, associated with diuretics or calcium antagonists, or both, in six patients to achieve optimal blood pressure control. Using a modified echo machine developed in the Institute of Clinical Physiology, Pisa, an on-line radio-frequency analysis was performed to obtain quantitative operator-independent measurements of the integrated backscatter signal of the ventricular septum and the posterior wall. The integrated values of the radio-frequency signal from the myocardial walls were normalized for those from the pericardial interface and were expressed as percentages (integrated backscatter index). RESULTS: In comparison with baseline, the treated hypertensives showed significant decreases in mean blood pressure, left ventricular mass index, and septal and posterior wall thickness. However, integrated backscatter index values were similar at baseline and after therapy for both the septum and the posterior wall. CONCLUSION: Antihypertensive therapy with enalapril does not increase myocardial reflectivity, although it does induce regression of left ventricular hypertrophy. This suggests that, in accord with experimental data, regression of hypertrophy is achieved by enalapril through a proportionate regression of the myocyte and connective tissue components of the myocardium.

Cardiomegaly↗