Hydrogen peroxide via thromboxane A2 receptors mediates myogenic response of small skeletal muscle veins in rats

We aimed to test two hypotheses: (1) isolated small veins develop substantial myogenic tone in response to elevation of intraluminal pressure, (2) H2O2 contributes to the mediation of myogenic response via activation of arachidonic acid (AA) cascade and release constrictor prostaglandins.

METHODS

Small veins were isolated from gracilis muscle of male rats, then cannulated. Changes of diameter to increases in intraluminal pressure, H2O2 and arachidonic acid in the presence and absence of various inhibitors were measured by videomicroscope and microangiometer. At the end of experiments the passive diameter were obtained in Ca2+ -free PSS solution.

RESULTS

Isolated rat gracilis muscle small veins developed a substantial myogenic tone in response to increases in intraluminal pressure (1-12 mmHg). Calculated maximum myogenic tone was 70 ± 5% at 10 mmHg. Presence of catalase or indomethacin or SQ 29,548 reduced significantly the pressure-induced myogenic response. Also, H2O2 (10-9-10-5 M) and arachidonic acid (10-7-10-4 M) elicited concentration dependent constrictions, which were inhibited by the presence of indomethacin or SQ 29,548.

CONCLUSION

We propose that both myogenic response and pressure-induced release of H2O2 play important roles in regulating the vasomotor function of venules both in physiological and pathological conditions.

Exercise testing and dipyridamole echocardiography test before and 48 h after successful coronary angioplasty: prognostic implications

The purpose of the present study was to determine the value of exercise testing (ET) and dipyridamole echocardiography test (DET) in the early functional evaluation after a successful coronary angioplasty (PTCA) and in the prediction of angina recurrence. 52 patients underwent ET and DET before and 48 h after a successful PTCA. During a 6-12 month follow-up period they all underwent clinical evaluation. Before PTCA, ET was positive in 49 of 52 patients (94%) and new asynergies were detected by DET in 47 of 52 patients (90%). 48 h after PTCA 23 patients (44%) had positive ET results and 10 had a positive DET response. During the follow-up, 17 patients experienced recurrence of angina. Positive predictive value (PPV) for angina recurrence of ET and DET performed early after the PTCA were, respectively, 57 and 80%. The PPV of ET increased to 88% when electrocardiographic (ECG) positivity was accompanied by angina. Negative predictive values of ET and DET were, respectively, 86% and 79%. Early after PTCA, exercise ECG positivity was not predictive of symptom recurrence while ECG positivity associated with angina revealed a high PPV, similar to that of DET.

Usefulness of high-dose dipyridamole echocardiography test in coronary angioplasty

Seventy-four consecutive patients with angina undergoing single-lesion percutaneous transluminal coronary angioplasty were evaluated with high-dose (up to 0.84 mg/kg during 10 minutes) dipyridamole echocardiography test (DET) before angioplasty and when possible, afterward. Angioplasty was clinically or angiographically successful in 63 patients and unsuccessful in 11. Before the procedure, 69 patients had a positive DET. Of these 69 patients, six with clinicall unsuccessful angioplasty had a dipyridamole time (i.e., the time from the onset of dipyridamole infusion to development of asynergy) lower than the 63 patients with clinically successfully angioplasty (4.2 +/- 2.9 vs. 7.0 +/- 2.9 minutes, mean +/- SD, p less than 0.01). In the five patients with angiographically unsuccessful angioplasty (residual stenosis diameter, greater than 50%), coronary stenosis decreased from 89 +/- 10 to 69 +/- 22 (p = NS); DET was positive in all five before and in four of the five after the procedure (100% vs. 80%, p = NS). In the 63 patients with angiographically successful angioplasty, coronary stenosis diameter was reduced from 85 +/- 9% to 30 +/- 10% (p less than 0.01). DET was positive in 58 patients before and in only 16 after the procedure (92% vs. 25%, p less than 0.01). In the 16 patients with positive DET, before and after angioplasty, dipyridamole time increased from 5.6 +/- 2.2 before to 7.3 +/- 2.4 minutes immediately after the procedure (p less than 0.05). After an average follow-up time of 10.8 +/- 5.9 months, angina recurred in eight of 47 patients with negative DET after angioplasty and in 11 of 16 patients with positive DET (17% vs. 69%, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

[Diagnostic reliability of clinical and instrumental data in identifying the presence of coronary disease in women with chest pain]

The present study was performed to assess the reliability of clinical symptom, rest and exercise electrocardiogram, exercise Thallium myocardial scintigraphy, as well as rest and exercise radionuclide angiocardiography, in order to detect significant coronary artery disease in 85 female patients with chest pain, who underwent coronary angiography. Of these, 54 underwent Thallium myocardial scintigraphy, 53 rest and exercise radionuclide angiocardiography. We have evaluated sensibility, specificity and positive and negative predictive value for each single variable or every possible combination. Within the population examined, Thallium myocardial scintigraphy reaches the highest sensibility (92%), specificity (92.5%), positive predictive (81%) and negative predictive value (97%). In comparison with all other clinical or instrumental parameters, taken either single or in combination. By subdividing the sample in two groups, of 20 and 65 patients respectively on the basis of the clinical symptom angina or thoracoalgy, with different predominance of coronaropathy (60 and 15%), Thallium myocardial scintigraphy is confirmed to be the most reliable diagnostic test (within the angina group sensibility 86%, specificity 100%, positive predictive value 100%, negative predictive value 83%, within the thoracoalgy group sensibility 100%, specificity 91%, positive predictive value 70%, negative predictive value 100%). However, within the thoracoalgy group, a negative maximal exercise test and a normal rest radionuclide angiocardiography detect patients with low probability of coronaropathy (negative predictive value respectively 100% and 93%). Within the angina group only Thallium myocardial scintigraphy significantly increases the predictive value of the angina symptom itself with respect to the presence of coronaropathy (positive predictive value of angina symptom alone 60%, of angina symptom plus Thallium myocardial scintigraphy 100%).