Inappropriate constriction of small coronary vessels as a possible cause of a positive exercise test early after successful coronary angioplasty

The diagnostic role of resting myocardial blood flow in STEMI patients after revascularization

Background

The value of semiquantitative resting myocardial perfusion imaging (MPI) in coronary artery disease (CAD) is limited. At present, quantitative MPI can be performed by a new cadmium zinc tellurium single-photon emission computed tomography (CZT-SPECT) scan. The quantitative index of resting myocardial blood flow (MBF) has received little attention, and its manifestations and clinical value in the presence of unstable coronary blood flow have not been clarified.

Purpose

In patients with ST-segment elevation myocardial infarction (STEMI), whether resting MBF can provide additional value of blood flow than semi-quantitative resting MPI is not sure. We also explored the influencing factors of resting MBF.

Methods

This was a retrospective clinical study. We included 75 patients with STEMI in the subacute phase who underwent resting MPI and dynamic scans after reperfusion therapy. General patient information, STEMI-related data, MPI, gated MPI (G-MPI), and resting MBF data were collected and recorded. According to the clinically provided culprit vessels, the resting MBF was divided into ischemic MBF and non-ischemic MBF. The paired Wilcoxon signed-rank test was used for resting MBF. The receiver operating characteristic (ROC) curves were used to determine the optimal threshold for ischemia, and multiple linear regression analysis was used to analyze the influencing factors of resting MBF.

Results

There was a statistically significant difference between the ischemic MBF and non-ischemic MBF [0.59 (0.47-0.72) vs. 0.76 (0.64-0.93), p < 0.0001]. The ROC curve analysis revealed that resting MBF could identify ischemia to a certain extent, with a cutoff value of 0.5975, area under the curve (AUC) = 0.666, sensitivity = 55.8%, and specificity = 68.7%. Male sex and summed rest score (SRS) were influencing factors for resting MBF.

Conclusion

To a certain extent, resting MBF can suggest residual ischemia after reperfusion therapy in patients with STEMI. There was a negative correlation between male sex, SRS, and ischemic MBF. A lower resting MBF may be associated with more severe myocardial ischemia.

Coronary Microvascular Spasm: Clinical Presentation and Diagnosis

Professor Maseri pioneered the research and treatment of coronary vasomotion abnormalities represented by coronary vasospasm and coronary microvascular dysfunction (CMD). These mechanisms can cause myocardial ischaemia even in the absence of obstructive coronary artery disease, and have been appreciated as an important aetiology and therapeutic target with major clinical implications in patients with ischaemia with non-obstructive coronary artery disease (INOCA). Coronary microvascular spasm is one of the key mechanisms responsible for myocardial ischaemia in patients with INOCA. Comprehensive assessment of coronary vasomotor reactivity by invasive functional coronary angiography or interventional diagnostic procedure is recommended to identify the underlying mechanisms of myocardial ischaemia and to tailor the best treatment and management based on the endotype of INOCA. This review highlights the pioneering works of Professor Maseri and contemporary research on coronary vasospasm and CMD with reference to endothelial dysfunction, Rho-kinase activation and inflammation.

Coronary microvascular dysfunction in stable ischaemic heart disease (non-obstructive coronary artery disease and obstructive coronary artery disease)

Diffuse and focal epicardial coronary disease and coronary microvascular abnormalities may exist side-by-side. Identifying the contributions of each of these three players in the coronary circulation is a difficult task. Yet identifying coronary microvascular dysfunction (CMD) as an additional player in patients with coronary artery disease (CAD) may provide explanations of why symptoms may persist frequently following and why global coronary flow reserve may be more prognostically important than fractional flow reserve measured in a single vessel before percutaneous coronary intervention. This review focuses on the challenges of identifying the presence of CMD in the context of diffuse non-obstructive CAD and obstructive CAD. Furthermore, it is going to discuss the pathophysiology in this complex situation, examine the clinical context in which the interaction of the three components of disease takes place and finally look at non-invasive diagnostic methods relevant for addressing this question.

Different vasoreactivity of arterial bypass grafts versus native coronary arteries in response to acetylcholine

BACKGROUND

Coronary angiography is often performed in patients with recurrent angina after successful coronary artery bypass grafting (CABG) in search of the progression of atherosclerosis. However, in many of these patients, no relevant stenosis can be detected. We speculate that coronary spasm may be associated with angina in these patients.

METHODS

From 2307 patients with unobstructed coronaries who underwent intracoronary acetylcholine spasm provocation testing (ACh-test) between 2012 and 2016, 54 consecutive patients who fulfilled the following inclusion criteria were included in this cohort study: previous left internal thoracic artery (LITA) bypass on the left anterior descending (LAD) coronary artery, ongoing/recurrent angina pectoris, no significant (< 50%) coronary artery or bypass stenosis. In all participants, the ACh-test was performed via the LITA bypass.

RESULTS

In 14 patients (26%) the ACh-test elicited epicardial spasm of the LAD distal to the anastomosis (≥ 90% diameter reduction with reproduction of the patient's symptoms and ischemic ECG shifts). Microvascular spasm (reproduction of symptoms and ischemic ECG-changes but no epicardial spasm) was seen in 30 patients (55%). The ACh-test was normal in the remaining 10 patients (19%). ACh-testing did not elicit any relevant vasoconstriction in the LITA bypasses in contrast to the LAD on quantitative coronary analyses (4.89 ± 7.36% vs. 52.43 ± 36.07%, p < 0.01).

CONCLUSION

Epicardial and microvascular coronary artery spasm are frequent findings in patients with ongoing or recurrent angina after CABG but no relevant stenosis. Vasoreactivity to acetylcholine is markedly different between LITA bypasses and native LAD arteries with vasoconstriction almost exclusively occurring in the LAD.

Role of endothelial dysfunction in determining angina after percutaneous coronary intervention: Learning from pathophysiology to optimize treatment

Endothelial dysfunction (EnD) is a hallmark feature of coronary artery disease (CAD), representing the key early step of atherosclerotic plaque development and progression. Percutaneous coronary intervention (PCI) is performed daily worldwide to treat symptomatic CAD, however a consistent proportion of patients remain symptomatic for angina despite otherwise successful revascularization. EnD plays a central role in the mechanisms of post-PCI angina, as it is strictly associated with both structural and functional abnormalities in the coronary arteries that may persist, or even accentuate, following PCI. The assessment of endothelial function in patients undergoing PCI might help to identify those patients at higher risk of future cardiovascular events and recurrent/persistent angina who might therefore benefit more from an intensive treatment. In this review, we address the role of EnD in determining angina after PCI, discussing its pathophysiological mechanisms, diagnostic approaches and therapeutic perspectives.

Prevalence of coronary macro- and micro-vascular dysfunctions after drug-eluting stent implantation without in-stent restenosis

BACKGROUND

The aim was to examine the prevalence and characteristics of epicardial vasomotor abnormality (EVA) and coronary microvascular dysfunction (CMD) including endothelium-dependent (EDCMD) or -independent (EICMD) in patients following a second-generation drug-eluting stent (second DES) implantation without in-stent restenosis.

METHODS AND RESULTS

In 105 patients who underwent second DES implantation in the left anterior descending coronary artery (74 men; mean age, 67.9±9.6years), and in 105 suspected angina patients without stenting (65 men; mean age 66.4±9.1years), we evaluated EVA using the acetylcholine provocation test, EDCMD and EICMD by measuring the coronary flow reserve and the relationship between myocardial ischemia (intracoronary lactate production between aorta and coronary sinus and ST-T changes) or recurrent angina and vascular function. There was no difference in the incidence of EVA between DES and control (49.5% versus 55.2%; P=0.41). Given that the prevalence of CMD was higher in DES than in control (59.0% versus 29.5%; P<0.001), CMD may be associated with stent placement. Of the CMD patients, EDCMD alone, EICMD alone, and both CMDs were found in 40.3%, 22.6%, and 37.1%, respectively. Myocardial ischemia was detected in 42.4% of patients, and recurrent angina was more common in the presence of both EDCMD and EICMD in patients with EVA or CMD compared to patients with normal vascular function (EVA, 42.9% versus 7.7%, P=0.015: CMD, 39.1% versus 7.7%, P=0.007).

CONCLUSIONS

Myocardial ischemia and recurrent angina may be caused by the presence of both EDCMD and EICMD after a second DES implantation without ISR.

Prediction of Post Percutaneous Coronary Intervention Myocardial Ischaemia

Following revascularisation the majority of patients obtain symptom relief and improved quality of life. However, myocardial ischaemia may recur or persist in a significant patient subset. Symptom recurrence is usually attributed to inaccurate evaluation of epicardial stenosis, incomplete revascularisation or stent failure and disease progression. However, technological advances with modern imaging and/or physiological evaluation of epicardial plaques have not solved this issue. Conversely, recent clinical studies have shown that abnormal coronary vasomotion and increased myocardial resistance are frequent determinants of post-percutaneous coronary intervention (PCI) myocardial ischaemia. Strategies to enhance prediction of post-PCI angina include proper selection of patients undergoing revascularisation, construction of clinical prediction models, and further invasive evaluation at the time of coronary angiography in those with high likelihood.

The no-reflow phenomenon: State of the art

Primary percutaneous coronary intervention (PCI) is the best available reperfusion strategy for acute ST-segment elevation myocardial infarction (STEMI), with nearly 95% of occluded coronary vessels being reopened in this setting. Despite re-establishing epicardial coronary vessel patency, primary PCI may fail to restore optimal myocardial reperfusion within the myocardial tissue, a failure at the microvascular level known as no-reflow (NR). NR has been reported to occur in up to 60% of STEMI patients with optimal coronary vessel reperfusion. When it does occur, it significantly attenuates the beneficial effect of reperfusion therapy, leading to poor outcomes. The pathophysiology of NR is complex and incompletely understood. Many phenomena are known to contribute to NR, including leukocyte infiltration, vasoconstriction, activation of inflammatory pathways and cellular oedema. Vascular damage and haemorrhage may also play important roles in the establishment of NR. In this review, we describe the pathophysiological mechanisms of NR and the tools available for diagnosing it. We also describe the microvasculature and the endothelial mechanisms involved in NR, which may provide relevant therapeutic targets for reducing NR and improving the prognosis for patients.

Recurrent angina after coronary angioplasty: mechanisms, diagnostic and therapeutic options

Recurrent angina in patients who underwent percutaneous coronary intervention is defined as recurrence of chest pain or chest discomfort. Careful assessment is recommended to differentiate between non-cardiac and cardiac causes. In the case of the latter, recurrent angina occurrence can be related to structural ('stretch pain', in-stent restenosis, in-stent thrombosis, incomplete revascularization, progression of coronary atherosclerosis) or functional (coronary micro-vascular dysfunction, epicardial coronary spasm) causes. Even though a complete diagnostic algorithm has not been validated, ECG exercise testing, stress imaging and invasive assessment of coronary blood flow and coronary vaso-motion (i.e. coronary flow reserve, provocation testing for coronary spasm) may be required. When repeated coronary revascularization is not indicated, therapeutic approaches should aim at targeting the underlying mechanism for the patient's symptoms using a variety of drugs currently available such as beta-blockers, calcium-channel blockers, ivabradine or ranolazine.

Reduced survival in patients with "coronary microvascular disease"

The syndrome of chest pain, abnormal stress test, and nonflow limiting coronary artery disease (CAD) is common and is attributed to coronary microvascular disease (µVD). It is associated with increased hospital admissions and health care costs. But its impact on long-term survival is not known. Of the 9941 consecutive patients who had an exercise stress test for evaluation of chest pain between May 1991 and July 2007, 935 had both a positive stress test and a coronary angiogram within 1 year of their stress test forming the study cohort. Significant angiographic CAD defined as ≥70% stenosis of an epicardial coronary artery or ≥50% stenosis of the left main coronary artery was present in 324 patients. Rest (n = 611) were considered to have coronary µVD. Compared with patients with significant epicardial CAD, patients with coronary µVD were younger (63 ± 11 vs. 65 ± 10 years, p = 0.002), and had lower left ventricular wall thickness (p < 0.02), systolic blood pressure (BP; p = 0.002), pulse pressure (0.0008), systolic BP with exercise (p = 0.0001), and pulse pressure with exercise (p < 0.0001). Those with coronary µVD had a better survival compared with those with significant epicardial CAD, but worse than that expected for age- and gender-matched population (p < 0.0001). Coronary µVD as a cause of chest pain and positive stress test is common. All-cause mortality in patients with coronary µVD is worse than in an age- and gender-matched population control, but better than those with significant epicardial CAD.

Microvascular coronary dysfunction in women: pathophysiology, diagnosis, and management

Women exhibit a greater symptom burden, more functional disability, and a higher prevalence of no obstructive coronary artery disease compared to men when evaluated for signs and symptoms of myocardial ischemia. Microvascular coronary dysfunction (MCD), defined as limited coronary flow reserve and/or coronary endothelial dysfunction, is the predominant etiologic mechanism of ischemia in women with the triad of persistent chest pain, no obstructive coronary artery disease, and ischemia evidenced by stress testing. Evidence shows that approximately 50% of these patients have physiological evidence of MCD. MCD is associated with a 2.5% annual major adverse event rate that includes death, nonfatal myocardial infarction, nonfatal stroke, and congestive heart failure. Although tests such as adenosine stress cardiac magnetic resonance imaging may be a useful noninvasive method to predict subendocardial ischemia, the gold standard test to diagnose MCD is an invasive coronary reactivity testing. Early identification of MCD by coronary reactivity testing may be beneficial in prognostication and stratifying these patients for optimal medical therapy. Currently, understanding of MCD pathophysiology can be used to guide diagnosis and therapy. Continued research in MCD is needed to further advance our understanding.

Role of coronary vasoconstriction in ischemic heart disease and search for novel therapeutic targets

Atherothrombosis has long been recognized as an important mechanism of cardiac events in ischemic heart disease, and large multicenter clinical studies have shown the benefit of antiplatelet agents, statins, beta-blockers and angiotensin converting enzyme inhibitors in preventing these events. However, more recent studies have been less successful at showing incremental gains in targeting these mechanisms, suggesting that the limits of this strategy have been exploited. Coronary vasoconstriction is another important mechanism in ischemic heart disease but has received little attention and yet is a potential therapeutic target. In the current review, the reasons why coronary vasconstriction has received insufficient consideration are explored. In particular, we need to change our approach from lumping heterogeneous clinical entities together to focusing on clinically-discrete homogeneous groups with a common mechanism and thus therapeutic target. The role of coronary vasoconstriction is examined in the various ischemic syndromes (variant angina, chronic stable angina, acute coronary syndromes and syndrome X) and the underlying mechanisms discussed. Finally, in order to advance studies in this field, an innovative research strategy is proposed, including: (1) selection of paradigmatic cases for the various ischemic syndromes; (2) candidate therapeutic targets; and (3) approaches in assessing the clinical efficacy of these potential therapies.

QT dispersion plus ST-segment depression: a new predictor of restenosis after successful percutaneous transluminal coronary angioplasty

BACKGROUND

ST-segment depression during exercise testing is frequently observed in the absence of restenosis after percutaneous transluminal coronary angioplasty (PTCA).

HYPOTHESIS

With the goal of improving the prediction of restenosis after PTCA, we evaluated the usefulness of ST-segment depression plus QT dispersion (QTd = QTmax - QTmin) during treadmill stress test.

METHODS AND RESULTS

Fifty-six patients (37 men, 19 women, mean age 51 +/- 14 years) were evaluated with treadmill exercise testing and coronary angiography 7 +/- 5 months after PTCA. Treadmill test was positive in 30 patients and negative in 26 patients. At coronary angiography, restenosis was present in 16 patients with positive exercise electrocardiogram (ECG) and in 6 patients with negative exercise ECG. Fourteen patients with a positive stress test did not have restenosis. There was no difference in QTd values between groups at baseline (p > 0.05). Exercise QTd was 63 +/- 9 ms in patients with positive exercise test, 54 +/- 18 ms in patients with negative exercise test (p = 0.003), 71 +/- 13 ms in patients with restenosis, and 53 +/- 17 ms in patients without restenosis (p = 0.001). ST-segment depression during the stress test determined restenosis with a sensitivity of 80% and a specificity of 58%. Sensitivity and specificity of QTd of > or = 60 ms for prediction of restenosis were 83 and 61%, respectively. When QTd of > or = 60 ms was added to ST-segment depression as a condition for positive test, the sensitivity and specificity increased to 91 and 78%, respectively. QT dispersion plus ST-segment depression had higher sensitivity and specificity than either QTd or ST-segment depression alone (p < 0.05).

CONCLUSION

The addition of QTd to ST-segment depression during exercise test improves the diagnostic value and can be used as a noninvasive tool in the diagnosis of restenosis after PTCA.

Pre-discharge exercise test for evaluation of patients with complete or incomplete revascularization following primary percutaneous coronary intervention: a DANAMI-2 sub-study

OBJECTIVES

It is unclear whether the completeness of revascularization impacts on the prognostic value of an exercise test after primary percutaneous coronary intervention (PCI).

METHODS

The DANAMI-2 trial included patients with ST elevation acute myocardial infarction randomized to primary PCI or fibrinolysis. Of the 790 patients randomized to primary PCI, 572 performed an exercise test. Prospectively, 310 patients were classified as having complete and 216 as having incomplete revascularization. Primary endpoint was a composite of reinfarction and/or death.

RESULTS

Patients with incomplete revascularization had lower exercise capacity [6.5 (95% CI: 1.9-12.8) vs. 7.0 (95% CI: 2.1-14.0) METs, p = 0.004] and more frequently ST depression [43 (20%) vs. 39 (13%), p = 0.02] compared to patients with complete revascularization. ST depression was not predictive of outcome in either groups, while multivariable analyses showed that exercise capacity was predictive of reinfarction and/or death in patients with incomplete revascularization [hazard ratio = 0.71 (95% CI: 0.54-0.93), p = 0.012] or of death alone [hazard ratio = 0.56 (95% CI: 0.41-0.77), p = 0.0003], which was not found in patients with complete revascularization.

CONCLUSIONS

Exercise capacity was prognostic of reinfarction and/or death in patients with incomplete revascularization, but not in completely revascularized patients. ST segment depression alone did not predict residual coronary stenosis or dismal prognosis.

Utility of routine exercise treadmill testing early after percutaneous coronary intervention

Background

There have been few prospective studies examining the utility of routine exercise treadmill testing (ETT) early after percutaneous coronary intervention (PCI). The objective of this study was to examine the impact of a routine ETT strategy early after PCI on follow-up cardiac events and procedures.

Methods

We examined 136 patients who underwent routine ETT at 6 weeks post-PCI in the ADORE trial. The ETT was classified as positive, indeterminate, or negative. The Duke Treadmill Score (DTS) was calculated for all patients. Follow-up occurred at 9 months.

Results

ETT results at 6 weeks were: 32 (23.5%) positive, 24 (17.6%) indeterminate and 80 (58.8%) negative. At 9 months, the composite event rate was 21.9% in those with a positive ETT, 20.8% in those with an indeterminate ETT and 12.5% in those with a negative ETT (p = 0.25 positive vs. negative ETT). The sensitivity of early ETT for predicting clinical events was 41.2%, the specificity was 73.3%, the positive predictive value was 21.9% and the negative predictive value was 87.5%. At 9 months, the cardiac procedure rate was 18.8% in those with a positive test, 13.0% in those with an indeterminate test, and 6.3% in those with a negative test (p = 0.07 positive vs. negative ETT). In a multivariate logistic regression model, coronary stenting during PCI and a ≥ 85% MPHR achieved were found to be inversely associated with clinical events. However, the DTS did not independently predict clinical events.

Conclusion

Although the statistical power of the study was limited by the small number of clinical events (particularly MI and death), the results of this study support the ACC/AHA guidelines that exercise treadmill testing should not be used routinely after PCI.

A QRS score versus ST-segment changes during exercise testing: which is the most reliable ischaemic marker after myocardial revascularisation?

BACKGROUND

The diagnostic ability of exercise testing based on ST-segment changes is low for the detection of restenosis after percutaneous transluminal coronary angioplasty (PTCA) or ischaemia after bypass surgery (CABG). The aim of this study was to improve the diagnostic accuracy of exercise testing in patients with a history of PTCA or CABG, with the implementation of a QRS score.

METHODS

We studied 128 post-PTCA patients (aged 49 +/- 8 years) and 104 post-CABG patients (aged 54 +/- 8 years), who had either positive exercise tests with or without angina, or negative exercise tests with continuing angina-like symptoms, and underwent cardiac catheterisation.

RESULTS

The univariate risk ratio of exercise-induced ST-segment deviation to detect restenosis was 3.05 (p = 0.005) and 0.83 (p = 0.690) in group A and group B patients, respectively. The univariate risk ratios of abnormal QRS score values to detect restenosis were 32.1 (p < 0.001) and 18.8 (p < 0.001) for group A and group B patients, respectively. The univariate risk ratios of the combination of exercise-induced ST-segment changes and of abnormal QRS score values to detect restenosis was 9.43 (p < 0.001) and 3.77 (p < 0.044) for group A and group B patients, respectively. The value of the area under the ROC curves is higher for the QRS score in group A patients, group B patients and for the whole study population.

CONCLUSIONS

QRS score values significantly improve the diagnostic ability of ST-segment change-based exercise testing, for the assessment of restenosis after PTCA or ischaemia after CABG.

The predictive value of exercise QRS duration changes for post-PTCA coronary events

BACKGROUND

The sensitivity and predictive values of exercise ECG testing using ST-T criteria after percutaneous transluminal coronary angioplasty (PTCA) are low, precluding its routine use for screening for restenosis. The predictive value of QRS duration criteria during exercise testing (ET) ECG after PTCA for future coronary events has not been reported. The aim of the study was to compare QRS duration changes with ST-T criteria during ET, as a predictor of coronary events after PTCA.

METHODS

A prospective study of 206 consecutive patients who underwent ET at a mean of 34 +/- 14 days after their first PTCA, and were the followed for a mean of 23 +/- 9 months. Patients were divided by QRS duration into two groups-Q1: ischemic response (QRS duration prolongation of more than 3 ms relative to the resting duration), and Q2: normal response (QRS duration shortening or without change from resting duration). Patients were also divided by their ST-T response, S1: ischemic response, and S2: normal response.

RESULTS

During follow-up 52 patients (58%) experienced restenosis or MI, or underwent CABG-Q1: 44 (85%), Q2: 8(15%) (P < 0.0002), S1: 8 (15%), S2: 44 (85%), (P < 0.641), two patients died-Q1: 1 (1%) and Q2: 1 (1%). For QRS and ST-T, the relative risk of having at least one of the coronary events was 4.02 (CI 2.1-9.9) versus 1.13 (CI 0.8-2.9), respectively. The sensitivity for future coronary events was 85% and 52% and the specificity was 48% and 98% for the QRS and ST-T criteria, respectively.

CONCLUSION

QRS prolongation during peak ET ECG after PTCA is a more sensitive marker than ST-T criteria for detection of patients at risk for later coronary events.

Limitation of coronary reserve after successful angioplasty is prevented by oral pretreatment with an alpha1-adrenergic antagonist

Coronary vasoconstriction that occurs after percutaneous transluminal coronary angioplasty (PTCA) is abolished by intracoronary phentolamine. An impairment of coronary vasodilator reserve (CVR) has been observed < or = 7 days after successful PTCA. To ascertain whether pretreatment with the alpha1-adrenergic receptor blocker doxazosin could prevent the limitation of CVR after PTCA, we carried out a randomised, double-blind, controlled study on 26 patients with significant (> 75%) single vessel disease undergoing PTCA. Twelve patients received doxazosin 4 mg daily in addition to their standard treatment, while 14 patients received matching placebo, starting 11 days before PTCA. Myocardial blood flow (MBF) at baseline and after i.v. dipyridamole (0.56 mg/kg) was measured within 5 days after PTCA using positron emission tomography (PET) with oxygen-15-labelled water. Angioplasty was successful in all patients with a residual stenosis < or = 35%. At PET scanning, hemodynamic parameters were comparable in the two groups. In the territory subtended by the dilated artery, CVR was significantly higher in patients treated with doxazosin compared with those receiving placebo (2.78 +/- 0.1.21 vs. 1.95 +/- 0.68; p < 0.01). Conversely, CVR in the remote territories subtended by angiographically normal arteries was similar in the two groups (2.53 +/- 0.92 and 2.48 +/- 0.80, respectively; p = NS). Treatment with oral doxazosin in addition to standard antianginal therapy can prevent the impairment of CVR frequently observed despite successful PTCA.

New evidence for the spasm-of-resistance-vessel concept of ischemic diseases

The spasm of resistance vessel (S-RV) concept of ischemic diseases avers that S-RV representing vascular autoregulatory dysfunction directly induces symptoms in ischemic diseases. The most important ischemic diseases, ischemic heart disease (IHD) and stroke, generally are not attributed to S-RV, and new evidence will be provided in this communication that S-RV induces IHD and stroke. Hypertension and the ischemic disorders of migraine and Raynaud's disease have been attributed to S-RV and to vascular dysregulation, and this information was used to help structure the study. It was found that these disorders are closely associated with IHD and stroke, and this is consistent with S-RV and vascular dysregulation as the mechanism for IHD and stroke. Also, it was found that multiple risk factors for IHD foster S-RV and are risk factors for hypertension, migraine, Raynaud's disease, and stroke, and this supports S-RV as the mechanism for IHD and stroke.

Influence of the endothelium, nitric oxide and serotonergic receptors on coronary vasomotor responses evoked by ergonovine in conscious dogs

1. The respective contributions of coronary vascular endothelium, nitric oxide (NO) and serotonergic receptors to the effects of ergonovine on large and small coronary arteries were investigated in conscious dogs. 2. In seven dogs with an endothelium intact, ergonovine (30 - 1000 microg, i.v.) induced a biphasic response on large coronary artery with an early and transient vasodilatation (up to +2.9+/-0.5% from 3310+/-160 microm, P<0.01) followed by a sustained vasoconstriction (down to -4.9+/-0.5%, P<0.001) which occurred simultaneously with a sustained increase in coronary blood flow (CBF) (up to +100+/-26% from 28+/-4 ml min(-1), P<0.001). After endothelium removal (balloon angioplasty), the ergonovine-induced vasodilatation was abolished and vasoconstriction potentiated (-6.4+/-0.9% after vs -4.9+/-0.5% before endothelium removal, P<0.01). 3. After blockade of NO synthesis by Nomega-nitro-L-arginine (30 mg kg(-1)) in four other dogs, the early vasodilatation induced by ergonovine was abolished but the delayed vasoconstriction as well as the increase in CBF remained unchanged. 4. Both ketanserin and methiothepin (0.3 mg kg(-1)) abolished the early vasodilatation and reduced the delayed vasoconstriction induced by ergonovine. Ketanserin decreased and methiothepin abolished the reduction in coronary resistance induced by ergonovine. 5. Thus, the complex interactions between vascular endothelium and serotonergic receptors to ergonovine-induced constriction of large coronary arteries might explain the induction of coronary spasms in patients with endothelial dysfunction.

Use of stress testing to evaluate patients with recurrent chest pain after percutaneous coronary revascularization

Controversy exists regarding the diagnostic accuracy, optimal technique, and timing of noninvasive stress testing after percutaneous transluminal coronary angioplasty (PTCA). Many patients return with chest pain after PTCA, and because the incidence of restenosis has been reported to be as high as 50%, a noninvasive test with a high predictive value is needed to reduce the need for unnecessary coronary angiography. Studies have shown that the sensitivity and specificity of stress testing varies depending on the amount of time elapsed since the procedure. Soon after a successful PTCA, perfusion defects on nuclear imaging following exercise or pharmacologic stress may be detected in asymptomatic patients without angiographic restenosis. In many patients, abnormal stress myocardial perfusion scans will normalize spontaneously, and thus stress testing with nuclear imaging within 4 to 6 weeks of PTCA lacks specificity for detecting restenosis. In contrast, stress echocardiography which detects wall motion abnormalities rather than perfusion mismatch has been reported to offer more specific information on myocardial ischemia and restenosis early after PTCA. In patients who develop chest pain more than 6 weeks after PTCA, the ability to accurately identify restenosis is shared by both echocardiographic and nuclear imaging methods. The purpose of this review is to clarify the strengths, pitfalls, and prognostic value of different stress modalities and cardiac imaging techniques in patients who develop chest pain within 6 months of undergoing PTCA.

Reliability of the exercise-induced ST-segment changes to detect restenosis three months after coronary angioplasty: significance of the appearance in other leads

BACKGROUND

Exercise-induced ST-segment changes 3 months after angioplasty may sometimes show a false-positive result.

METHODS

We therefore analyzed the ST changes observed during the exercise tests performed before and 3 months after angioplasty in 118 patients with single-vessel coronary artery disease.

RESULTS

Ninety-two (78%) of the 118 patients had ST changes in the same lead before and after angioplasty, whereas the remaining 26 (22%) patients had ST changes in other leads in the postangioplasty test when compared with the preangioplasty exercise test. Restenosis was found in 44 (48%) of the 92 patients with ST changes in the some lead but in only four (15%) of the 26 patients with ST changes in other leads.

CONCLUSIONS

Exercise-induced ST-segment changes are not reliable markers of restenosis 3 months after angioplasty. ST-segment changes observed in other leads after angioplasty compared with the preangioplasty exercise test may show a false-positive result.

Reliability of exercise-induced ST segment changes to detect restenosis 3 months after coronary angioplasty: significance of the appearance in other leads

Exercise-induced ST-segment changes 3 months after angioplasty sometimes may show a false-positive result. We therefore analyzed the ST changes observed during the exercise tests performed before and 3 months after angioplasty in 118 patients with single-vessel coronary artery disease. Ninety-two (78%) of the 118 patients had ST changes in the same lead before and after angioplasty, whereas the remaining 26 (22%) patients had ST changes in other leads in the postangioplasty exercise test when compared with the preangioplasty test. Restenosis was found in 44 (48%) of the 92 patients with ST changes in the same lead but in only 4 (15%) of the 26 patients with ST changes in other leads. We conclude that exercise-induced ST segment changes are not reliable markers of restenosis 3 months after angioplasty. ST segment changes observed in other leads after angioplasty may show a false-positive result when compared with the preangioplasty exercise test.

Diagnostic value of exercise electrocardiography and angina after coronary artery stenting. Benestent Study Group

To determine whether metallic stent implantation within a coronary artery modifies the accuracy of angina or exercise test results in predicting stenosis, we studied 172 patients assigned to stent implantation and 153 patients assigned to balloon angioplasty enrolled in the Benestent trial comparing de novo stenting with conventional balloon angioplasty. Sensitivity and specificity curves were constructed for the prediction of percentage diameter stenosis and minimal lumen diameter. Receiver-operator curves were constructed for comparison of diagnostic accuracy. Identical exercise load and duration were achieved in the two groups, despite a better angiographic result in patients treated with a stent. Similarly, the diagnostic accuracy of clinical symptoms or exercise test results as a function of the angiographic results were similar in patients with and patients without a stent. The intersection points of the sensitivity and specificity curves for recurrent angina or ST-segment depression were 72% to 77%. The corresponding cut-off points for percentage diameter stenosis were, respectively, 52% and 50% for patients with and without a stent (1.35 and 1.50 mm for minimal lumen diameter). We conclude that the presence of an intracoronary stent does not affect the diagnostic accuracy of recurrent angina or exercise-induced ST depression in predicting residual stenosis. We also conclude that exercise tolerance is similar after balloon angioplasty, with or without stenting, despite a better angiographic outcome in the group receiving a stent, suggesting a minimal threshold beyond which the patient is no longer at risk for ischemia during exercise.

The value of exercise electrocardiography testing in the identification of coronary restenosis: a probability analysis

We studied by means of probability analysis the role of exercise ECG in identifying coronary restenosis. A total of 213 patients were independently evaluated by clinical history, conventional assessment of the exercise ECG ('yes or no' statement), D score (a discriminant function derived from exercise ECG), and coronariography, 5.4 +/- 2.8 months after successful coronary angioplasty. The initial probability of restenosis (30%), that is, the prevalence of the condition, was radically changed by the result of clinical history (77% for patients with angina vs. 17% for those without angina). By contrast, ECG binary assessment, due to its low accuracy (70% vs 82% of clinical history, P < 0.005), was unable to significantly change the established probabilities after symptomatic evaluation. Finally, D score, which greatly enhanced specificity (92% vs. 76% of bivariate assessment, P < 0.0001), proved to be useful in changing the probability (from 32% to 76% or to 25%) of patients (n = 34) with a discordant result (no angina/positive exercise ECG). When this stepwise approach was tested in 46 new patients, predicted and observed probabilities were actually very similar. We conclude that exercise ECG has a very limited role in identifying coronary restenosis if positive responses are not adjusted with a weighted score which takes into account other exercise derived factors.

Exercise-induced ST-segment depression in patients without restenosis after coronary angioplasty. Relation to preprocedural impaired left ventricular function

BACKGROUND

ST-segment depression during exercise testing is frequently observed in the absence of restenosis after coronary angioplasty.

METHODS AND RESULTS

We studied the determinants of this phenomenon in 70 consecutive patients with unstable angina related to a single left anterior descending coronary artery lesion who had successful angioplasty without restenosis (< 50% stenosis by quantitative angiography). We compared preangioplasty clinical, angiographic, and hemodynamic variables in the group with positive (ExT Pos, n = 35; ST depression, 2.3 +/- 0.9 mm) and negative (ExT Neg, n = 35; ST depression, 0.3 +/- 0.5 mm) results on exercise testing at follow-up angiography. At this time, minimal lumen diameter (1.7 +/- 0.4 mm) and mean residual stenosis (34 +/- 11%) in the ExT Pos group were not significantly different from the values (1.9 +/- 0.5 mm, 38 +/- 10%) in the ExT Neg group. Before angioplasty, the ExT Pos group had a lower ejection fraction (63 +/- 8% versus 68 +/- 9%, P < .05), more marked anterior hypokinesis estimated by the extent of anterior wall contraction on quantitative ventriculography (P < .05), and a greater end-systolic volume (30 +/- 11 versus 25 +/- 9 mL/m2, P < .05) than the ExT Neg group. At follow-up angiography, regional anterior wall motion was normal in 68 patients (97%). Anterior hypokinesis before angioplasty was strongly associated (P < .01) with a positive exercise test at control (71% compared with 31% in patients with normal wall motion before angioplasty).

CONCLUSIONS

In the absence of significant epicardial stenosis after angioplasty, ST-segment depression is strongly associated with the presence of preprocedural regional ventricular dysfunction that has recovered at follow-up angiography.

Response of human coronary arteries to serotonin after injury by coronary angioplasty

BACKGROUND

Atherosclerotic stenoses that have exaggerated vasomotor responses are especially prone to restenosis after coronary angioplasty. Experimental studies show that vasomotor responses in normal vessels are altered by acute mechanical injury, an alteration that in part reflects changes in the functional characteristics of endothelium that has regenerated after injury.

METHODS AND RESULTS

We examined, by quantitative coronary arteriography, the response of dilated and control coronary segments to intracoronary infusions of graded doses of serotonin, an endothelium-dependent vasoactive agent, and to intracoronary injection of isosorbide dinitrate, an endothelium-independent smooth muscle dilator in 15 patients who had undergone a single percutaneous transluminal coronary angioplasty procedure and who had no clinical features of variant angina. Dose-dependent constriction to serotonin occurred at all measured sites. The mean +/- SEM diameter reductions, expressed as percent reduction in baseline diameter that was observed at proximal (18.1 +/- 2.9, 18.8 +/- 2.2) and distal (30.9 +/- 4.4, 35.4 +/- 5.3) control sites in the dilated and nondilated vessels, respectively, at the highest dose, were similar. The degree of constriction in distal segments was significantly (P < .01) greater than that in proximal segments. Total or subtotal occlusion occurred at the angioplasty site in 4 patients at the highest infused dose (10(-4) mol/L). The mean percent reduction in baseline diameter at previously dilated sites (53.8 +/- 5.9) at this dose was significantly (P < .05) greater than that observed at the adjacent proximal control sites and similar to that observed at distal control sites. All segments dilated significantly after intracoronary injection of isosorbide dinitrate.

CONCLUSIONS

In dilated and nondilated vessels, serotonin caused significantly more marked constriction in distal than in proximal vessel segments. In dilated vessels, the vessel segments that had been subjected to angioplasty had a constrictor response to serotonin that was more marked than at adjacent proximal control sites and equivalent to that in the distal vessel segments. This enhanced constrictor response could be related to changes in endothelial cell function after regeneration or to hyperreactivity of smooth muscle cells at the angioplasty site.

Restenosis after coronary angioplasty

Coronary angioplasty is used to treat coronary disease in many patients. Indications for angioplasty have expanded since it was first performed, mainly as a result of improvement in equipment and techniques. One problem with coronary angioplasty is the phenomenon of renarrowing of the treated coronary lesion, a process called restenosis. The events that constitute restenosis appear to be a universal response to the arterial wall injury of angioplasty. They are currently characterized as follows: platelet adhesion and aggregation on the damaged endothelium and within deep splits into the tunica media; release of platelet-derived growth factors; inflammation of the mechanically injured medial zone; transformation of smooth muscle cells of the tunica media after their activation by several of the growth-promoting substances; migration and proliferation of transformed smooth muscle cells, with secretion of copious amounts of extracellular matrix material; and, finally, termination of the growth process with regrowth of endothelium over the injured area. A decade of research work has helped identify clinical correlates of restenosis after coronary angioplasty procedures. This work is hindered by lack of a uniform angiographic definition of restenosis. In addition, much of the information has come from small studies, with incomplete follow-up and retrospective orientation. Nevertheless, some data are available. Patient-related correlates include male gender, unstable angina, diabetes, and continued smoking after angioplasty. Lesion-related correlates include multilesional and multivessel procedures, higher postangioplasty residual stenosis, proximal vessel location, location in the left anterior descending artery, location in a vein graft, long lesions, and total occlusions. The only consistent procedure-related correlate has been incorrect sizing of the angioplasty balloon to the treated artery. For the purposes of individual patient care, clinical correlates are not helpful. No group of variables has been found to be associated with complete freedom from restenosis, and no group is completely predictive of restenosis. All patients undergoing angioplasty procedures require some follow-up through subsequent months and years. Symptom status and the results of noninvasive studies have been investigated for purposes of follow-up. Symptoms are virtually useless by themselves for predicting restenosis or its absence. When symptom status is combined with exercise thallium 201 scintigraphy performed 4 to 6 months after an angioplasty procedure, the two factors are less than ideal but have a negative predictive value of more than 90%. This means that more than 90% of patients who have neither symptoms nor evidence of ischemia by thallium 201 scintigraphy will not have angiographic restenosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Restenosis after coronary angioplasty

Coronary angioplasty is used to treat coronary atherosclerotic disease in many patients. One problem with coronary angioplasty is the phenomenon of restenosis. Restenosis appears to be a universal response to arterial wall injury. The biological events that underlie restenosis are characterized by: platelet adhesion and aggregation at sites of damaged endothelium, and within dissections into the medial layers, release of platelet derived growth-promoting substances, inflammation of the injured medial zone, transformation, migration, and proliferation of smooth muscle cells of the media following their activation by growth-promoting substances, secretion of copious amounts of extracellular matrix material, and finally, termination of the growth process following regrowth of endothelium over the damaged area. More than a decade of research work has helped identify clinical correlates of restenosis after coronary angioplasty. Patient-related correlates include male gender, unstable angina, diabetes, and continued smoking after angioplasty. Lesion-related correlates include multilesion and multivessel procedures, higher post-angioplasty residual stenosis, proximal vessel location, location in the left anterior descending coronary artery, location in a vein graft, long lesions, and total occlusions. However, for the purposes of individual patient care, clinical correlates are not particularly helpful. No group of variables has predicted complete freedom from restenosis, and conversely no group of variables has reliably indicated its presence. All patients undergoing angioplasty will require some form of follow-up evaluation. Symptom status by itself has not been found to be useful for predicting restenosis. However, when symptom status is combined with exercise thallium-201 scintigraphy, performed 4-6 months after angioplasty, it is less than ideal, but has a negative predictive value of over 90%. This means that over 90% of patients who are asymptomatic and have no evidence of ischemia by thallium-201 scintigraphy, will not have angiographic restenosis. Numerous clinical trials have been performed in order to reduce or prevent restenosis. Almost all have been disappointing, while a few have been encouraging. Studies of antiplatelet agents such as aspirin, dipyridamole (Boehringer Ingelheim Pharmaceuticals Inc., Ridgefield, CT, USA), and Ticlopidine (Syntex, Humgcao, Puerto Rico) have not shown efficacy, yet studies of an inhibitor of platelet-derived growth factor have been provocatively encouraging. No reduction in restenosis rates was found with the anticoagulants Coumadin (Du Pont Pharmaceuticals, Wilmington, DE, USA) and Heparin (Wyeth-Ayerst, Philadelphia, PA, USA). Fish oils (omega fatty acids) have been found in several clinical trials to provide modest, but encouraging, reductions in restenosis, but await further confirmation.(ABSTRACT TRUNCATED AT 400 WORDS)

Alteration in regulation of myocardial blood flow in one-vessel coronary artery disease determined by positron emission tomography

The behavior of myocardial blood flow (MBF) regulation in territories supplied by angiographically normal vessels of patients with coronary artery disease (CAD) has been poorly investigated. Resting MBF and coronary reserve were evaluated in 32 patients with stable angina, no previous myocardial infarction, and isolated left anterior descending or left circumflex coronary artery stenosis (> or = 50% diameter narrowing). MBF was measured, in the absence of any medical therapy, by means of dynamic positron emission tomography and 13N-ammonia. MBF measurements at baseline and after intravenous dipyridamole (0.56 mg/kg administered over 4 minutes), were obtained both in the stenosis-related regions and in contralateral territories. As a control group, 14 normal subjects were evaluated according to the same protocol. At rest, the 32 patients with CAD had similar MBF values in the stenotic and remote regions (0.76 +/- 0.21 and 0.77 +/- 0.19 ml/min/g, respectively, p = NS); both these values were significantly (p < 0.01) reduced with respect to mean MBF in normal subjects (1.03 +/- 0.25 ml/min/g). The dipyridamole study was completed in 30 patients; these patients had lower values of maximal MBF in the stenotic than in the remote regions (1.52 +/- 0.65 vs 1.76 +/- 0.68 ml/min/g, p < 0.05); however, both these values were significantly reduced (p < 0.01) with respect to mean dipyridamole MBF in normal subjects (3.66 +/- 0.92 ml/min/g). Thus, in patients with CAD, resting and maximal MBF can be reduced not only in myocardial territories supplied by stenotic arteries, but also in territories supplied by angiographically normal arteries.

Endothelium dependent and independent responses in coronary artery disease measured at angioplasty

OBJECTIVE--To investigate the effects of substance P and papaverine, two drugs that increase coronary blood flow by different mechanisms, on vasomotion in stenotic coronary arteries at percutaneous transluminal coronary angioplasty (PTCA). DESIGN--Coronary blood flow responses to substance P and papaverine were measured in stenotic coronary arteries at the time of PTCA with quantitative angiography and a Doppler flow probe. SETTING--A cardiothoracic referral centre. PATIENTS--15 patients undergoing elective PTCA of a discrete epicardial coronary artery stenosis. INTERVENTIONS--Pharmacological coronary flow reserve was determined with papaverine 5-10 minutes before and after successful PTCA. Endothelium dependent responses to 2 minute infusions of substance P (10-15 pmol.min-1) were assessed immediately before PTCA. MAIN OUTCOME MEASURES--Coronary blood flow responses and changes in epicardial coronary artery area at stenotic, proximal, and distal sites with papaverine and substance P. RESULTS--Stenotic sites dilated with papaverine before PTCA (17.7%(6.9%) (mean (SEM)) area increase, p < 0.05 v baseline). Substance P dilated stenotic sites (16.8%(5.7%) area increase, p < 0.05) and proximal (14.3%(5.4%), p < 0.05) and distal sites (41.7%(9.3%), p < 0.005). Coronary flow reserve increased but did not reach normal values after PTCA (2.3(0.4) before PTCA v 3.0(0.4) after PTCA, p < 0.05) and was associated with an increase in peak flow with papaverine. Angioplasty did not alter baseline flow. After PTCA papaverine caused significant vasoconstriction at the stenotic site (-13.6%(4.3%) area decrease, p < 0.05). There was a negative correlation (r = -0.68, p < 0.05) between the dilator response with papaverine before PTCA and the constrictor response after PTCA. CONCLUSIONS--Substance P causes endothelium dependent dilatation in atheromatous coronary arteries, even at sites of overt atheroma. The cause of the paradoxical constrictor response to papaverine after PTCA is uncertain, but unopposed flow mediated vasoconstriction (the myogenic response) after balloon induced endothelial denudation may be one of several contributory factors.

Response of human coronary arteries to acetylcholine after injury by coronary angioplasty

OBJECTIVES

The aim of this study was to investigate the effect of intracoronary administration of acetylcholine on large epicardial vessels 8 days after successful coronary angioplasty.

BACKGROUND

Intracoronary infusion of acetylcholine causes vessel dilation in patients without angiographic evidence of coronary atherosclerosis, whereas it causes constriction of stenotic coronary branches. These findings were interpreted as evidence of endothelial dysfunction in patients with coronary atherosclerosis.

METHODS

Eight patients who underwent successful single-vessel coronary angioplasty of the proximal left anterior descending artery were studied. Eight days after coronary angioplasty at the time of follow-up coronary angiography, intracoronary acetylcholine was infused (1 ml/min for 2 min) at concentrations ranging from 10(-7) to 10(-4) mol/liter. The diameter of the angioplasty and distal segments of the left anterior descending artery and that of the proximal and distal segments of the circumflex artery (control artery) were measured using computerized edge detection angiography.

RESULTS

All patients showed a dose-dependent constriction in response to acetylcholine and experienced chest pain and ST segment changes. Intracoronary nitroglycerin (300 micrograms) relieved the effects of acetylcholine. The maximal tolerated dose of acetylcholine (10(-6) mol/liter in three patients, 10(-5) mol/liter in three patients and 10(-4) mol/liter in two patients) induced a mild constriction of the angioplasty segment from 1.84 +/- 0.11 mm to 1.52 +/- 0.13 mm (p < 0.02) similar to that of the proximal segment of the control artery (from 2.42 +/- 0.23 to 2.07 +/- 0.19 mm, p < 0.02). However, the degree of constriction of the vascular segments distal to the angioplasty site (from 1.24 +/- 0.09 to 0.62 +/- 0.13 mm, p < 0.01) was significantly greater (p < 0.05) than that observed in the distal segments of the control artery (from 1.23 +/- 0.03 to 0.71 +/- 0.01 mm, p < 0.01) and resulted in transient total occlusion in two patients.

CONCLUSIONS

Eight days after coronary angioplasty, coronary segments distal to the dilated site but not at the dilated site are hyperreactive to acetylcholine. The response of epicardial coronary arteries to acetylcholine is influenced not only by the dose of acetylcholine and the endothelial function (as currently believed) but also by the location of the coronary segment considered, confirming the presence of a profound alteration of distal coronary vessels.