Effects of A1 adenosine receptor blockade on the warm-up phenomenon

The increased tolerance to myocardial ischemia observed during the second of two sequential exercise tests, i.e. the warm-up phenomenon, has been proposed as a clinical model of ischemic preconditioning. Adenosine appears to be a mediator of ischemic preconditioning in both experimental and clinical settings. The purpose of this study was to investigate the role of A1 adenosine receptors in the warm-up phenomenon. A double-blind, placebo-controlled, cross-over design was used. Twelve patients with coronary artery disease and positive exercise test were randomized to receive either bamiphylline, a selective A1 adenosine receptor antagonist, or placebo, immediately prior to two consecutive treadmill exercise tests carried out on day 1. Then, on day 2 all patients underwent two consecutive exercise tests immediately after administration of the remaining treatment. During the first exercise test, bamiphylline, compared to placebo, increased the time to and rate-pressure product at 1.5 mm ST-segment depression (from 317 +/- 118 to 423 +/- 127 s, p < 0.05 and from 199 +/- 38 to 230 +/- 36 b/min.mmHg.10(2), p < 0.05, respectively). After both placebo and bamiphylline infusions, time to 1.5 mm ST-segment depression during the second exercise test was greater than that during the first test (445 +/- 121 vs 317 +/- 118 s, p < 0.001 and 483 +/- 128 vs 423 +/- 127 s, p < 0.05, respectively), as was rate-pressure product at 1.5 mm ST-segment depression (228 +/- 40 vs 199 +/- 38 b/min.mmHg.10(2), p < 0.01 and 253 +/- 42 vs 230 +/- 36 b/min.mmHg.10(2), p < 0.05, respectively). In conclusion, bamiphylline, at a dose able to increase ischemic threshold and exercise tolerance compared to placebo, does not prevent the warm-up phenomenon. These findings suggest that, in the setting of the warm-up phenomenon, A1 adenosine receptor blockade is insufficient to prevent ischemic preconditioning.

A comparison of coronary-artery stenting with angioplasty for isolated stenosis of the proximal left anterior descending coronary artery

BACKGROUND

Randomized studies have shown that the use of coronary-artery stenting as the initial treatment for coronary stenosis is associated with a lower risk of restenosis than is standard coronary angioplasty. We prospectively investigated the efficacy of these two approaches in selected patients with isolated stenosis of the proximal left anterior descending coronary artery.

METHODS

A total of 120 patients with isolated stenosis of the proximal left anterior descending coronary artery were randomly assigned to stent implantation or standard coronary angioplasty. The primary clinical end points were the rate of procedural success (defined as residual stenosis of less than 50 percent and the absence of death, myocardial infarction, and the need for coronary-artery bypass surgery during the hospital stay) and the rate of event-free survival (defined as freedom from death, myocardial infarction, and the recurrence of angina) at 12 months. The angiographic end point was the rate of restenosis 12 months after the procedure.

RESULTS

The two treatment groups did not differ significantly with respect to demographic, clinical, or angiographic characteristics. The rates of procedural success were similar in the two groups of patients (95 percent in the stenting group vs. 93 percent in the angioplasty group, P = 0.98). The 12-month rates of event-free survival were 87 percent after stenting and 70 percent after angioplasty (P = 0.04). The rates of restenosis were 19 percent after stent implantation and 40 percent after angioplasty (P = 0.02).

CONCLUSIONS

In patients with symptomatic isolated stenosis of the proximal left anterior descending coronary artery, stenting had advantages over standard coronary angioplasty in that it was associated with both a lower rate of restenosis and a better clinical outcome.

Effects of bamiphylline on exercise testing in patients with syndrome X

An abnormal stimulation of adenosine A1-receptors has been suggested to play a role in the pathogenesis of both chest pain and ischemia-like electrocardiographic changes in patients with syndrome X and a nonselective adenosine antagonist (theophylline) has been reported to be beneficial in these patients. In this study we investigated the acute effects of bamiphylline, a specific A1-receptor antagonist, in 16 patients with syndrome X (14 women, age 57 +/- 6 years), with both angina and ST-segment depression inducible during exercise testing. All patients underwent two treadmill exercise tests (Bruce modified protocol) on 2 separate days, 5 minutes after the end of randomized intravenous infusion of either placebo (saline solution) or bamiphylline (300 mg). Severity of chest pain was assessed by a 100 mm visual analogic scale. There were no significant differences in resting heart rate and blood pressure after bamiphylline or placebo. Rate-pressure product (20 600 +/- 5000 vs 20 200 +/- 5200 bpm.mmHg), time to 1 mm ST depression (549 +/- 196 vs 581 +/- 201 sec), time to angina (519 +/- 209 vs 571 +/- 196 sec), and exercise duration (717 +/- 134 vs 676 +/- 166 sec) were also not significantly different after bamiphylline or placebo, but there was a mild reduction of the severity of exercise-induced chest pain (30 +/- 22 vs 39 +/- 20 mm, p < 0.05) with the active drug. Thus, in patients with syndrome X, bamiphylline does not improve exercise-induced ST changes, suggesting that A1-receptors are not significantly involved in their appearance. In addition, bamiphylline had little effect on anginal pain, suggesting that this cannot be mediated exclusively by A1-receptor stimulation in these patients.

Differences of regional coronary flow reserve assessed by adenosine thallium-201 scintigraphy early and six months after successful percutaneous transluminal coronary angioplasty or stent implantation

This study assesses regional coronary flow reserve using adenosine thallium-201 scintigraphy early and 6 months after angiographically successful percutaneous transluminal coronary angioplasty (PTCA) or stent implantation. Seventeen consecutive men with a significant isolated left anterior descending coronary artery stenosis were scheduled for repeat coronary angiography and adenosine-planar thallium-201 scintigraphy within 24 hours and 6 months after successful PTCA (n = 8) or stent implantation (n = 9). After background subtraction, left ventricular segmental uptake was semiquantitatively assessed on thallium images. The perfusion defect severity was scored from 0 (normal) to 3. Coronary angiograms were analyzed using an automated edge contour detection computer analysis system. Data are expressed as mean value +/- 1 SD, and proportions as percentage. The residual narrowing was 17 +/- 8% after PTCA and 9 +/- 2% after stent implantation (p = 0.02). Twenty-four hours after the procedure, hypoperfused segments were detected in all patients (100%) and in 4 patients (44%) (p = 0.05), respectively. The total number of hypoperfused segments was greater after PTCA than after stent implantation (16 [40%] vs 7 [16%], p = 0.001, respectively) as was the perfusion defect severity (4.4 +/- 3.1 vs 1 +/- 1.2, p = 0.006). Six months after the procedure, 3 of the 5 patients who had undergone PTCA without restenosis still had reversible perfusion defects. None of the stent-treated patients had restenosis or reversible perfusion defects (p = 0.05). Among PTCA-treated patients without restenosis, the total number of hypoperfused segments and the perfusion defect severity were 9 of 25 (36%) and 0.8 +/- 0.8, respectively. Thus, a regional reduction in coronary flow reserve, occasionally observed early after successful stent implantation, is probably due to a transient alteration of small coronary vessels, as was also supported by the absence of perfusion defects 6 months after the procedure. The more severe impairment of regional coronary flow reserve observed early after successful PTCA is probably also due to angiographic underestimation of the residual stenosis, as suggested also by the persistence of reversible perfusion defects 6 months after the procedure in a few patients.

Mechanisms of the warm-up phenomenon

The warm-up phenomenon, described in patients with coronary artery disease, refers to the improved performance following a first exercise test. The aim of this study was to investigate the causes of the warm-up phenomenon. Fifteen patients with coronary artery disease and positive exercise test were enrolled. Patients were off treatment throughout the study. They underwent two consecutive treadmill exercise tests according to the Bruce protocol, with a recovery period of 10 min to re-establish baseline conditions. A third exercise test was then performed 2 h later. Before the onset of ischaemia, the rate-pressure product for a similar degree of workload was similar during the first and second exercise test, while it was lower during the third test (P < 0.05). Time to 1.5 mm ST-segment depression during the second and third exercise test was greater than during the first test (454 +/- 133 and 410 +/- 161 vs 354 +/- 127 s, P < 0.01, respectively). Similarly, the time to anginal pain onset was increased during the second and third exercise tests, compared to the first test (356 +/- 208 and 310 +/- 203 vs 257 +/- 204 s, P < 0.01, respectively). In contrast, rate-pressure product at 1.5 mm ST-segment depression during the second test was higher than that during the first test (232 +/- 47 vs 210 +/- 39 beats.min-1.mmHg.10(2), P < 0.01), while in the third test it was similar to that during the first (209 +/- 43 beats.min-1.mmHg.10(2), P = ns). The warm-up phenomenon observed a few minutes after exercise is characterized by an increase of both time to ischaemia and ischaemic threshold; this adaptation to ischaemia may be due to an improvement of myocardial perfusion or to preconditioning. Conversely, the warm-up phenomenon observed a few hours after repeated exercise is characterized by an increase of time to ischaemia but not of ischaemic threshold and is caused by a slower increase of cardiac workload. Thus, the mechanisms of the warm-up phenomenon may be different, time dependent and related to previous training.

Effects of A1 adenosine receptor blockade by bamiphylline on ischaemic preconditioning during coronary angioplasty

OBJECTIVE

The role of A1 adenosine receptors in preconditioning in humans is unknown. To establish whether bamiphylline, a selective antagonist of A1 adenosine receptors, abolishes ischaemic preconditioning in man, 36 consecutive patients undergoing single-vessel coronary angioplasty were randomized to receive intravenous infusion of bamiphylline (5 mg.kg-1) or placebo (0.9% NaCl) immediately prior to the procedure.

DESIGN

The mean values (+/- 1 SD) of ST segment shifts on the surface and intracoronary electrocardiograms were measured at the end of the first and second balloon inflations, both 2 min long. The severity of cardiac pain was obtained at the same time using a visual analogue scale.

RESULTS

In bamiphylline-treated patients, the mean ST segment shift and the severity of cardiac pain during the second inflation were similar to those during the first inflation (14 +/- 15 vs 16 +/- 16 mm, ns and 31 +/- 28 vs 31 +/- 29, ns, respectively). Conversely, in placebo-treated patients both the mean ST segment shift and the severity of cardiac pain during the second inflation were significantly less than those during the first inflation (10 +/- 6 vs 17 +/- 7 mm, P < 0.001 and 25 +/- 21 vs 39 +/- 31 mm, P < 0.01, respectively). Thus, bamiphylline abolishes ischaemic preconditioning observed in man during repeated coronary balloon inflations.

CONCLUSION

These results suggest that, in this setting, ischaemic preconditioning is mediated, at least in part, by A1 adenosine receptors.

Early postoperative myocardial ischemia after coronary artery bypass grafting. Detrimental effects of nitroglycerine infusion

This study was aimed at assessing the incidence and mechanisms of myocardial ischemia early after coronary artery bypass grafting and the effects of treatment with nitroglycerine. The electrocardiogram of 35 patients (29 males and 6 females, mean age 61 +/- 8 years) with stable angina and multivessel coronary disease, was monitored continuously for 24 hours after uncomplicated coronary artery bypass grafting. Patients were randomized to receive nitroglycerin infusion or placebo. Fourteen of the 35 patients (40%) had 24 transient ischemic episodes (mean duration 11.8 +/- 3.5 min; range 6-20 min with ST segment elevation in 6, ST segment depression in 7 and both ST segment elevation and depression in 1. Seventy-five per cent of the ischemic episodes occurred within the first 6 postoperative hours. The mean ejection fraction prior to surgery and the mean number of stenosed vessels and of the implanted grafts were similar in patients with and without postoperative ischemia (57 +/- 5 vs 57 +/- 6%, p = 0.86; 2.7 +/- 0.5 vs 2.8 +/- 0.4, p = 0.52 and 3.0 +/- 0.9 vs 3.2 +/- 0.7, p = 0.51, respectively) as well as total bypass time and cross-clamp time (123 +/- 38 vs 124 +/- 18 min, p = 0.89 and 67 +/- 20 vs 70 +/- 14 min, p = 0.68, respectively). The values of heart rate and systolic blood pressure at the onset of the ischemic episodes were similar to those recorded 15 min before (103 +/- 16 vs 106 +/- 18 b/min, p = 0.36 and 119 +/- 12 vs 121 +/- 14 mmHg, p = 0.48). Ischemic episodes were recorded in 9 of the 16 patients (56%) randomized to receive nitroglycerine and in 5 only of the 19 patients (26%) randomized to receive placebo (p = 0.05). Thus, transient ischemic episodes occurring early after coronary artery bypass grafting are not preceded by an increase in myocardial oxygen consumption; they appear to be due, therefore, to a primary reduction in coronary blood flow. Treatment with nitroglycerine is associated with a higher prevalence of ischemic episodes, thus suggesting that myocardial ischemia is unlikely to be caused by spasm of large epicardial vessels or grafts. Myocardial ischemia may be caused, instead, by extracorporeal circulation-induced alterations enhanced by the hypotensive effects of nitroglycerine.

Risk factors in patients with different clinical and angiographic manifestations of ischemic heart disease

In patients who present with unheralded myocardial infarction both the severity and the extent of coronary atherosclerosis appear to be less than that in patients with chronic stable angina, thus suggesting that, in the latter, protective factors may prevent or delay the evolution towards acute coronary syndromes. Therefore, risk factors were compared in 88 consecutive patients (73 men; mean age 56 +/- 9 years) with unheralded myocardial infarction and a single, discrete, > 70% stenosis in the proximal right, left circumflex or left anterior descending coronary artery (Group 1) and in 55 consecutive patients (46 men; mean age 58 +/- 9 years with chronic stable angina and multiple, diffuse, > 70% stenoses localized both in the right and left coronary arteries (Group 2). Continuous data are presented as mean value +/- 1 SD, proportions as percentages. In Group 1 mean serum levels of total cholesterol, low-density lipoprotein cholesterol and triglycerides were similar to those in mg/dl, p = 0.93 and 160 +/- 87 vs 155 +/- 76, p = 0.74, respectively) while the mean serum level of high-density lipoprotein cholesterol was higher in Group 2 (49 +/- 4 vs 46 +/- 4 mg/dl, p = 0.005). The prevalence of a positive family history of ischemic heart disease, hypertension and smoking habit were similar in the two groups, while the prevalence of diabetes mellitus was higher in Group 2 (29 vs 6%, p = 0.001). Thus, in patients with otherwise similar coronary risk factors, higher levels of high-density lipoprotein cholesterol and diabetes mellitus appear to be associated with a reduced tendency of coronary atherosclerosis to cause acute coronary syndromes.

Muscular and cardiac adenosine-induced pain is mediated by A1 receptors

OBJECTIVES

This study attempted to establish whether bamiphylline, a selective antagonist of A1 adenosine receptors, prevents the algogenic effects of adenosine in humans.

BACKGROUND

Experimental findings indicate that the sympathoexcitatory response elicited by adenosine is mediated by A1 receptors.

METHODS

An intrailiac infusion of increasing doses (from 125 to 2,000 micrograms/min) of adenosine was given to 20 patients. Adenosine infusion was then repeated after intrailiac infusion of either bamiphylline or saline solution. In 14 other patients with angina, increasing doses of adenosine (from 108 to 1,728 micrograms/min) were infused into the left coronary artery. Adenosine infusion was then repeated after the intravenous infusion of either bamiphylline or placebo. Coronary blood flow velocity was monitored by a Doppler catheter. Data relative to pain severity are expressed as median and all other data as mean value +/- 1 SD.

RESULTS

Bamiphylline prolonged the time to pain onset caused by the intrailiac adenosine infusion from 444 +/- 96 to 749 +/- 120 s (p < 0.001) and reduced pain severity from 45 to 24 mm (p < 0.01). After placebo infusion, the time to pain onset and pain severity were similar to that of baseline (428 +/- 112 vs. 430 +/- 104 s, p = 0.87 and 44 vs. 43 mm, p = 0.67, respectively). Bamiphylline prolonged the time to pain onset caused by intracoronary adenosine infusion from 519 +/- 128 to 603 +/- 146 s (p < 0.01) and reduced pain severity from 58 to 28 mm (p < 0.02). After placebo infusion, the time to pain onset and pain severity were similar to that at baseline (542 +/- 87 vs. 551 +/- 79 s, p = 0.14 and 55 vs. 50 mm, p = 0.61). Maximal coronary blood flow velocities before and after bamiphylline administration were similar (47 +/- 22 vs. 49 +/- 24 cm/s, p = 0.36) as well as before and after placebo administrtion (40 +/- 20 vs. 41 +/- 20 cm/s, p = 0.07).

CONCLUSIONS

Bamiphylline reduces adenosine-induced muscular and cardiac pain but does not affect adenosine-induced coronary vasodilation. These findings indicate that at the dose used in this study, bamiphylline does not detectably block vascular A2-receptor-mediated adenosine effects in humans, which suggests that the muscular and cardiac algogenic effects of adenosine are mediated mainly by A1 receptors.

Determinants of myocardial ischemia during percutaneous transluminal coronary angioplasty in patients with significant narrowing of a single coronary artery and stable or unstable angina pectoris

Previous studies have assessed the determinants of collateral vessel recruitment during coronary occlusion in patients undergoing percutaneous transluminal coronary angioplasty (PTCA). However, the determinants of severity of myocardial ischemia after sudden coronary occlusion do not necessarily coincide with those responsible for collateral vessel recruitment. The aim of this study was to assess the determinants of severity of myocardial ischemia during balloon inflation by recording surface and intra-coronary electrocardiograms (ECGs). In 62 consecutive patients with 1-vessel disease and without previous myocardial infarction undergoing successful PTCA for stable (n = 33) or unstable (n = 29) angina pectoris, the summation of the absolute values of ST-segment shifts from baseline on the intracoronary and surface ECG at the end of the first 2-minute inflation was obtained as an index of the severity of myocardial ischemia. Stenosis severity before PTCA was measured using computerized coronary angiography, while the grade of collateral filling was scored according to Rentrop's classification. The mean (+/- 1 SD) ST-segment shift at the end of balloon inflation was less in patients with than without collateral vessels (12 +/- 10 vs 23 +/- 15 mm, p < 0.05). Despite a similar prevalence of collateral vessels (34% vs 24%, p = NS), the mean ST-segment shift was also less in patients with unstable than stable angina (15 +/- 9 vs 24 +/- 17 mm, p < 0.05). However, the mean ST-segment shift was not associated with the severity of coronary stenosis before PTCA (r = 0.0004, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Substance P potentiates the algogenic effects of intraarterial infusion of adenosine

OBJECTIVES

This study investigated whether substance P potentiates the muscular and cardiac pain caused by the intraarterial infusion of adenosine, an autocoid known to induce muscular and cardiac ischemic-like pain in humans.

BACKGROUND

Substance P is involved in the generation of neurogenic inflammation and causes cutaneous hyperalgesia. Because substance P is present in perivascular nerves it might also cause muscular and cardiac hyperalgesia. To test this hypothesis its effects on adenosine-induced muscular and cardiac pain were investigated in humans.

METHODS

A randomized, crossover study of the algogenic effects of the intrailiac infusion of increasing scalar doses (from 125 to 2,000 micrograms/min) of adenosine or substance P (11.2 pmol/min) for 3 min, followed by the simultaneous infusion of substance P plus the same doses of adenosine, was carried out in nine patients with no evidence of peripheral vascular disease. A similar protocol was carried out by infusing increasing scalar doses of adenosine (from 50 to 800 micrograms/min) or substance P (11.2 pmol/min) for 3 min, followed by the simultaneous infusion of substance P plus the same doses of adenosine, into the left coronary artery of eight patients with angina. Pain severity, assessed by a visual analog scale, is presented as median. The remaining data are presented as mean value +/- 1 SD.

RESULTS

All patients experienced pain during both adenosine and substance P plus adenosine infusion; no patient experienced pain during the infusion of substance P alone. During intrailiac infusion, all patients experienced pain in the right leg that occurred earlier (207 +/- 152 vs. 321 +/- 154 s, p < 0.05) and was greater (47 vs. 30 mm, p < 0.05) during the simultaneous infusion of substance P plus adenosine than during the infusion of adenosine. Similarly, during intracoronary infusion, all patients experienced chest pain that occurred earlier (409 +/- 242 vs. 596 +/- 210 s, p < 0.05) and was greater (51 vs. 33 mm, p < 0.05) during the simultaneous infusion of substance P plus adenosine than during infusion of adenosine. No patient exhibited electrocardiographic signs of ischemia.

CONCLUSIONS

Substance P does not cause muscular or cardiac pain, but it provokes muscular and cardiac hyperalgesia.

Ischemic preconditioning during coronary angioplasty is prevented by glibenclamide, a selective ATP-sensitive K+ channel blocker

BACKGROUND

Brief episodes of ischemia render the heart more resistant to subsequent ischemia; this phenomenon has been called ischemic preconditioning. In some animal species, myocardial preconditioning appears to be due to activation of ATP-sensitive K+ (KATP) channels. The role played by KATP channels in preconditioning in humans remains unknown. The aim of this study was to establish whether glibenclamide, a selective KATP channel blocker, abolishes the ischemic preconditioning observed in humans during coronary angioplasty following repeated balloon inflations.

METHODS AND RESULTS

Twenty consecutive patients undergoing one-vessel coronary angioplasty were randomized to receive 10 mg oral glibenclamide or placebo. Sixty minutes after glibenclamide or placebo administration, patients were given an infusion of 10% dextrose (8 mL/min) to correct glucose plasma levels or, respectively, an infusion of saline at the same infusion rate. Thirty minutes after the beginning of the infusion, both patient groups underwent coronary angioplasty. The mean values (+/- 1 SD) of ST-segment shifts on the surface 12-lead ECG and the intracoronary ECG were measured at the end of the first and second balloon inflations, both 2 minutes long. In glibenclamide-treated patients, the mean ST-segment shift during the second balloon inflation was similar to that observed during the first inflation (23 +/- 13 versus 20 +/- 8 mm, P = NS), and the severity of cardiac pain was greater (55 +/- 21 versus 43 +/- 23 mm on a scale of 0 to 100, P < .05). Conversely, in placebo-treated patients the mean ST-segment shift during the second inflation was less than that during the first inflation (9 +/- 5 versus 23 +/- 13 mm, P < .001), as was the severity of cardiac pain (15 +/- 15 versus 42 +/- 19 mm, P < .01). Blood glucose levels were significantly reduced 60 minutes after glibenclamide compared with those at baseline (53 +/- 9 versus 102 +/- 10 mg/100 mL, P < .001) in the glibenclamide group; however, before coronary angioplasty, blood glucose levels increased to 95 +/- 19 mg/100 mL, a value similar to that found in placebo group (96 +/- 11 mg/100 mL, P = NS).

CONCLUSIONS

In humans, ischemic preconditioning during brief repeated coronary occlusions is completely abolished by pretreatment with glibenclamide, thus suggesting that it is mainly mediated by KATP channels.

Evidence of cardiac suction in the presence of high end-diastolic filling pressure: a case report

Cardiac suction has been previously demonstrated in the normal heart and in cardiac diseases characterized by a normal or reduced end-diastolic ventricular pressure. We report a patient with tight mitral stenosis and severe tricuspid regurgitation who provides the evidence of cardiac suction, despite the presence of increased end-diastolic pressures. The negative diastolic pressures observed in our patient appear to be related to the preservation of a vigorous contraction of both ventricles resulting in small end-systolic volumes. In this setting the elastic potential energy stored in the myocardium during each vigorous contraction is released during diastole, thus creating a negative pressure which sucks blood into the ventricles.

Mechanisms of cardiac pain during coronary angioplasty

OBJECTIVES

This study was conducted to establish whether the cardiac pain patients experience during coronary angioplasty is modulated by 1) the stretching of the coronary artery wall, and 2) the mechanisms responsible for the ischemic preconditioning.

BACKGROUND

Anecdotal experimental observations indicate that stretching of the coronary artery wall is a stimulus adequate to cause cardiac pain. Furthermore, recent experimental studies indicate that adenosine, a mediator of the anginal pain, appears to play an important role in the genesis of ischemic preconditioning.

METHODS

We randomly allocated 48 consecutive patients undergoing coronary angioplasty into two groups. In Group A the second balloon inflation was performed at a higher level than the first; in Group B the first two inflations were performed at the same level of balloon pressure. The mean values (+/- 1 SD) of ST segment shift on the surface 12-lead electrocardiogram (ECG) and the intracoronary ECG were measured at the end of each inflation period. Severity of cardiac pain was also obtained at the same time by using a visual analog scale.

RESULTS

The mean ST segment shift during the second balloon inflation was significantly less than that during the first inflation in both groups of patients (12.8 +/- 9.3 vs. 18.5 +/- 11.9 mm, p < 0.001 and 13.7 +/- 10.1 vs. 21.3 +/- 13.9 mm, p < 0.001, respectively, in Groups A and B). Yet, the severity of cardiac pain during the second inflation was greater than that during the first inflation in Group A (40.8 +/- 32.7 vs. 26.9 +/- 27.2 mm, p < 0.01), whereas it was lesser in Group B (23.1 +/- 20.7 vs. 32.9 +/- 29.6 mm, p < 0.05). However, in the latter group, pain severity after normalization for the mean ST segment shift was similar during the first and second inflations (2.1 +/- 2.4 vs. 2.7 +/- 3.6, p = NS).

CONCLUSIONS

During coronary angioplasty, the cardiac pain experienced by patients is caused in part by stretching of the coronary artery wall. If the stretching is maintained at a constant level during repeated coronary occlusions, the cardiac pain is entirely predicted by the severity of myocardial ischemia and therefore does not appear to be directly modulated by the mechanisms responsible for the ischemic preconditioning.

Left ventricular volumes during exercise in normal subjects and patients with dilated cardiomyopathy assessed by first-pass radionuclide angiography

During isotonic exercise, left ventricular (LV) suction and the Frank-Starling law of the heart may have important roles in the enhancement of early LV diastolic filling and in the increase of myocardial contractility, respectively. It remains controversial whether these mechanisms operate in normal subjects or patients with dilated cardiomyopathy. Ten healthy subjects and 10 patients with idiopathic dilated cardiomyopathy who underwent maximal upright bicycle exercise testing were studied. First-pass radionuclide angiography was performed at both rest and peak exercise using a multicrystal gamma camera. In normal subjects, LV end-systolic volume at peak exercise was smaller than during baseline (17 +/- 7 vs 30 +/- 15 ml/m2; p < 0.05), whereas rapid filling volume was greater (52 +/- 16 vs 38 +/- 8 ml/m2; p < 0.01). In patients with dilated cardiomyopathy, both end-systolic (108 +/- 34 to 123 +/- 53 ml/m2; p = NS) and rapid filling (24 +/- 6 to 28 +/- 9 ml/m2; p = NS) volumes did not change from rest to peak exercise. A significant correlation was found between the changes in end-systolic volume at peak exercise and in peak rapid filling rate in normal subjects (r = 0.6; p < 0.05), but not in patients with dilated cardiomyopathy (r = 0.3; p = NS). In normal subjects, end-diastolic volume at peak exercise was similar to that during baseline (78 +/- 14 and 85 +/- 15 ml/m2, respectively; p = NS), whereas in patients with dilated cardiomyopathy, it was greater (164 +/- 50 vs 146 +/- 33 ml/m2; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged asymptomatic catheter-induced left and right coronary artery spasm resistant to high dose of intracoronary nitroglycerin

A 58-year-old woman, referred to our hospital to undergo invasive assessment of mitral valve stenosis, demonstrated prolonged asymptomatic catheter-induced left anterior descending and right coronary artery spasm during coronary arteriography. Coronary spasms were not associated with ECG and arterial blood pressure changes. Intracoronary injection of nitroglycerin (300 and 600 micrograms bolus) did not resolve coronary spasm. Coronary angiography, repeated 24 hours later using the same procedure and materials, did not show any evidence of coronary artery spasm. The present clinical case is interesting for 3 reasons. First, the presence of prolonged proximal double-vessel coronary spasm not associated with symptoms or signs of acute myocardial ischemia; second, the incapacity of high dose of intracoronary nitroglycerin to resolve the coronary spasm; third, the dramatic changes in the sensitivity of coronary artery to mechanical stimulation in different days.

Peak exercise left ventricular performance in normal subjects and in athletes assessed by first-pass radionuclide angiography

The role of Frank-Starling law of the heart in determining the increase in cardiac output during exercise in humans is still controversial (e.g., the mechanisms responsible for the enhancement of left ventricular [LV] filling during the shortened diastolic interval). Ten weight lifters, 12 swimmers and 12 sedentary subjects who underwent maximal upright bicycle exercise testing were studied. First-pass radionuclide angiography was performed both at rest and at peak exercise using a multicrystal gamma camera. Compared with resting values, heart rate and cardiac index at peak exercise increased by 101 +/- 16 beats/min (p less than 0.001) and 6.7 +/- 2.8 liters/min/m2 (p less than 0.001) in weight lifters, by 96 +/- 9 beats/min (p less than 0.001) and 9.5 +/- 2 liters/min/m2 (p less than 0.001) in swimmers, and by 103 +/- 9 beats/min (p less than 0.001) and 7.3 +/- 1.8 liters/min/m2 (p less than 0.001) in sedentary subjects. Stroke volume increased by 20.5 +/- 9.8 ml/m2 (p less than 0.001) in swimmers only. End-diastolic volume at peak exercise did not change in weight lifters and in swimmers; it decreased by 8.2 +/- 8.6 ml/m2 (p less than 0.01) in sedentary subjects. A significant correlation was found between the decrease in end-systolic volume and the increase in peak rapid filling rate at peak exercise in all 3 groups (r = 0.65, p less than 0.05 in weight lifters; r = 0.59, p less than 0.05 in swimmers; r = 0.67, p less than 0.05 in sedentary subjects.(ABSTRACT TRUNCATED AT 250 WORDS)