Effects of long-term treatment with 120 mg of sustained-release isosorbide dinitrate and 60 mg of sustained-release nifedipine on myocardial perfusion

Medication and ECG Patterns That May Hinder SPECT Myocardial Perfusion Scans

Coronary artery disease (CAD) is the leading cause of death followed by cancer, in men and women. With risk factors being endemic and the increasing costs of healthcare for management and treatment, myocardial perfusion imaging (MPI) finds a central role in risk stratification and prognosis for CAD patients, but it comes with its limitations in that the referring clinician and managing team must be aware of and use at their advantage. This narrative review examines the utility of myocardial perfusion scans in the diagnosis and management of patients with ECG alterations such as atrioventricular block (AVB), and medications including calcium channel blockers (CCB), beta blockers (BB), and nitroglycerin which may impact the interpretation of the exam. The review analyzes the current evidence and provides insights into the limitations, delving into the reasons behind some of the contraindications to MPI.

Study of the possible medical and medication explanatory factors of angiographic outcomes in patients with acute ST elevation myocardial infarction undergoing primary percutaneous intervention

Background:

Myocardial blush grade (MBG), thrombolysis in myocardial infarction (TIMI) and corrected TIMI frame count (cTFC) are indices of successful angiographic reperfusion. This study sought to determine the predictors of angiographically successful reperfusion including demographic, clinical and angiographic factors in patients with ST elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI).

Materials and Methods:

A cross-sectional study of patients with a confirmed diagnosis of STEMI undergoing pPCI was designed. Eligible patients referring to a university heart center were enrolled in the study from March 2012 to December 2012. Successful epicardial reperfusion was defned as TIMI flow grade 3 or cTFC<= 28 frames and successful myocardial reperfusion as MBG 2 or 3.

Results:

The study population consisted of 100 patients, including 74 males and 26 females, with mean ± standard deviation age of 58.27 ± 11.60 years. Achieving open microvasculature (MBG 2/3) was positively associated with a history of nitrate intake (P = 0.03) and history of calcium channel blocker (CCB) intake (P = 0.005). Hyperglycemia was inversely associated with achieving a final cTFC ≤ 28 frames (r = −0.32, P = 0.001).

Conclusions:

Our findings suggest that patients with a history of nitrate and CCB intake had a higher likelihood of successful PCI. In addition, patients with a higher blood glucose level on admission may have a reduced rate of reperfusion success. Future studies with a larger sample size are recommended to investigate the significant relationships observed in this study.

Sequential single-photon emission computed tomography myocardial perfusion imaging

The utility of stress myocardial perfusion imaging (MPI) for the diagnosis and prognosis of coronary artery disease (CAD) has been firmly established in numerous clinical studies and has become an essential component of clinical practice. Stress MPI is now used regularly to guide initial risk stratification and management of patients with CAD. Because stress MPI provides an assessment of the physiologic significance of CAD, it is a particularly attractive procedure for assessing follow-up risk. Today, sequential stress MPI is being used increasingly to track disease progression, assess follow-up risk, detect restenosis following revascularization, and evaluate the efficacy of aggressive medical therapy and risk-factor modification. By providing serial snapshots of the disease and its impact on perfusion, sequential stress MPI may alter treatment decisions and ultimately improve long-term patient management and outcomes. Use of sequential stress MPI to detect changes in perfusion following surgical or medical therapies is being tested currently in the Clinical Outcomes Using Revascularization and Aggressive Drug Evaluation (COURAGE) and Adenosine Sestamibi Single-Photon Emission Computed Tomography Postinfarction Evaluation (INSPIRE) trials.

Risk assessment by myocardial perfusion imaging for coronary revascularization, medical therapy, and noncardiac surgery

Stress myocardial perfusion imaging (MPI) has become an important tool in risk stratification of patients with known coronary artery disease. A normal myocardial perfusion scan has a high negative predictive value and is associated with low annual mortality rate (< 1%). Patients with extensive ischemia (> 20% of the left ventricle), defects in more than 1 coronary vascular territory, transient or persistent left ventricular cavity dilation, and ejection fraction less than 45% have a high annual mortality rate (> 3%). Those patients should undergo coronary revascularization whenever feasible, as the cardiac event rate increases in proportion to the magnitude of the jeopardized myocardium. Stress MPI can be used to demonstrate ischemia in patients with symptoms early after coronary artery bypass surgery (< 5 years) or in those without symptoms late (>/= 5 years) after coronary artery bypass surgery. With respect to patients who underwent percutaneous interventions, stress MPI can help detect in-stent restenosis early after the intervention (3-6 months) or assess the progression of native coronary disease afterward. Since preliminary data suggest that a reduction in the perfusion defect size may translate to a reduction of coronary events, stress MPI can help assess the efficacy of medical management of coronary disease. Finally, stress MPI is indicated for perioperative cardiac risk stratification for noncardiac surgery in patients with intermediate risk predictors (mild angina, prior myocardial infarction or heart failure symptoms, diabetes mellitus, renal insufficiency) and poor functional capacity or in those who undergo high-risk surgery with significant implications in further preoperative management.

Effects of medical therapy on outcome assessment using exercise thallium-201 single photon emission computed tomography imaging: evidence of a protective effect of beta-blocking antianginal medications

OBJECTIVES

The purpose of this study was to determine whether antianginal medications modify the prognostic significance of exercise single photon emission computed tomography (SPECT) ischemia.

BACKGROUND

Antianginal medications (especially beta-adrenergic blocking agents) limit exercise SPECT ischemia, but it is not known whether such medications also modify the prognostic effect of exercise SPECT ischemia.

METHODS

We included 352 patients with coronary heart disease, who had exercise Tl-201 SPECT and coronary angiography, and who were initially treated medically. Survival Cox models were applied in patients for whom classes of antianginal medications taken at exercise SPECT were the same as those prescribed for follow-up (GI; n = 136), and in patients for whom new classes of antianginal medications, including beta-blockers (GII; n = 79) or not including beta-blockers (GIII; n = 113), were added for follow-up.

RESULTS

During a mean 5.3+/-1.6 years of follow-up, 45 patients had cardiac death or myocardial infarction. Variables reflecting necrosis (irreversible defect extent, left ventricular ejection fraction) and those from coronary angiography provided equivalent prognostic information in the three groups. In contrast, the SPECT variable reflecting ischemia (reversible defect extent), which provided comparable prognostic information in GI (p = 0.005) and GIII (p = 0.004), lost its prognostic significance (p = 0.54) in GII, and was associated with a lower relative risk in GII than in GI or GIII (both p < 0.05).

CONCLUSIONS

In patients with coronary heart disease, the introduction of antianginal medications, when including beta-blockers, appears to have a favorable effect on the deleterious prognostic effect of exercise ischemia.

Intensive medical therapy versus coronary angioplasty for suppression of myocardial ischemia in survivors of acute myocardial infarction: a prospective, randomized pilot study

BACKGROUND

Patients who have inducible ischemia after acute myocardial infarction (AMI) generally undergo coronary angiography with the intent to revascularize. Whether this approach is superior to intensive treatment with anti-ischemic medications is unknown.

METHODS AND RESULTS

We performed a prospective, randomized pilot study comparing intensive medical therapy with coronary angioplasty (PTCA) for suppression of myocardial ischemia in 44 stable survivors of AMI. Myocardial ischemia was quantified with adenosine 201Tl tomography (SPECT) performed 4.5+/-2.9 days after AMI. All patients at baseline had a large total (>/=20%) and ischemic (>/=10%) left ventricular perfusion defect size (PDS). SPECT was repeated at 43+/-26 days after therapy was optimized. The total stress-induced PDS was comparably reduced with medical therapy (from 38+/-13% to 26+/-16%; P<0.0001) and PTCA (from 35+/-12% to 20+/-16%; P<0.0001). The reduction in ischemic PDS was also similar (P=NS) in both groups. Cardiac events occurred in 7 of 44 patients over 12+/-5 months. Patients who remained clinically stable had a greater reduction in ischemic PDS (-13+/-9%) than those who had a recurrent cardiac event (-5+/-7%; P<0.02). Event-free survival was superior in the 24 patients who had a significant (>/=9%) reduction in PDS (96%) compared with those who did not (65%; P=0.009).

CONCLUSIONS

In this small pilot study, intensive medical therapy and PTCA were comparable at suppressing ischemia in stable patients after AMI. Sequential imaging with adenosine SPECT can track changes in PDS after anti-ischemic therapies and thereby predict subsequent outcome. Corroboration of these preliminary findings in a larger cardiac-event trial is warranted.

Achieving sustained improvement in myocardial perfusion: role of isosorbide mononitrate

The efficacy of antianginal agents in the treatment of patients with chronic stable angina has traditionally been evaluated by performance measures, such as the exercise treadmill test (ETT). Although reliable and reproducible, ETT is not a sensitive measure of changes in myocardial ischemia. The effects of antianginal agents on coronary blood flow and myocardial perfusion have been less frequently studied. Angiographic studies have demonstrated that nitrates may operate by preferentially directing blood flow to ischemic regions of the myocardium. These investigations have been limited, however, by the invasive nature of the evaluation. Measurements of regional myocardial perfusion may also be made with noninvasive tests. Both quantitative single-photon emission computed tomography (SPECT) and positron emission tomography (PET) have been employed, but few studies have used these techniques to assess the effects of antianginal drugs (in general) and nitrates (in particular) on changes in reversible myocardial perfusion defects. Studies that have evaluated the direct effects of nitrate treatment on coronary blood flow and myocardial perfusion defects in patients with chronic stable angina are reviewed, and preliminary data from a study of the effects of long-term nitrate treatment on myocardial perfusion are discussed.

Evaluation of diabetic patients for renal and pancreas transplantation: noninvasive screening for coronary artery disease using radionuclide methods

Pharmacologic stress thallium scintigraphy is commonly performed in the risk assessment of diabetic patients with nephropathy before kidney and/or pancreas transplantation; however, controversy exists regarding the test's accuracy in detecting coronary artery disease. Our purpose was to compare pharmacologic stress thallium scintigraphy and also exercise radionuclide ventriculography with coronary angiography in diabetic patients undergoing evaluation for transplantation. In addition, we also determined the association of the test results with outcome after transplantation. The medical records of 47 patients (mean age, 37+/-9 years) without clinical evidence of coronary artery disease were reviewed. Forty-one patients had pharmacologic stress thallium scintigraphy performed during their evaluation. Sensitivity was 62% and specificity was 76% for detecting > or = 75% coronary artery stenosis (sensitivity was 53% and specificity was 73% for > or = 50% stenosis). Thirty-five patients had exercise radionuclide ventriculography performed. Sensitivity was 50% and specificity was 67% for detecting > or = 75% coronary artery stenosis (sensitivity was 44% and specificity was 63% for > or = 50% stenosis). Thirty patients had both pharmacologic stress thallium scintigraphy and exercise radionuclide ventriculography performed; when either test was abnormal, sensitivity in the detection of > or = 50% or > or = 75% stenosis tended to increase compared with pharmacologic stress thallium scintigraphy alone (0.05<P<0.10), whereas specificity decreased (P<0.01). The incidence of adverse cardiac outcomes was identical for patients with abnormal thallium scintigrams and undergoing transplantation (2/11) compared with patients with normal scintigrams and undergoing transplantation (4/22). We conclude that: (1) pharmacologic stress thallium scintigraphy and exercise radionuclide ventriculography are suboptimal screening tests for coronary artery disease in diabetic patients awaiting kidney and/or pancreas transplantation; (2) using the two radionuclide tests in combination results in a decrease in specificity; and (3) patients with abnormal thallium scintigrams can receive transplants with outcomes similar to those for patients with normal thallium scintigrams.

Transdermal nitroglycerin patch therapy reduces the extent of exercise-induced myocardial ischemia: results of a double-blind, placebo-controlled trial using quantitative thallium-201 tomography

OBJECTIVES

This study prospectively evaluated whether transdermal nitroglycerin patches could limit the extent of exercise-induced left ventricular ischemia as assessed by quantitative thallium-201 tomography.

BACKGROUND

Although antianginal medications are effective at reducing chest pain symptoms in patients with coronary artery disease, there is limited evidence that these agents can also reduce myocardial ischemia.

METHODS

This was a randomized, double-blind, parallel, placebo-controlled trial evaluating nitroglycerin patch therapy in patients in stable condition with angiographic coronary artery disease and no previous myocardial infarction. All patients were weaned from antianginal agents and had a baseline symptom-limited treadmill test followed by thallium-201 tomography. Forty patients with perfusion defects involving > or = 5% of the left ventricle were randomized to receive either intermittent (12 h on/off) active nitroglycerin patch therapy (0.4 mg/h) or placebo. Exercise tomography was repeated a mean (+/- SD) of 6.1 +/- 1.8 days after randomization.

RESULTS

Patients randomized to receive active patch therapy had a significant reduction in their total perfusion defect size (-8.9 +/- 11.1%) compared with placebo-treated patients (-1.8 +/- 6.1%, p = 0.04), which was most apparent in those with the largest (> or = 20%) baseline perfusion defects (-11.4 +/- 13.4% vs. 1.0 +/- 3.6%, respectively, p < 0.02). Furthermore, 7 (33%) of 21 patients receiving active therapy had a > or = 10% decrease in their perfusion defects compared with only 1 (5%) of 19 patients randomized to receive placebo (p = 0.002). Nitrate therapy did not significantly reduce heart rate, blood pressure or double product, indicating benefit through enhancement of coronary blood flow.

CONCLUSIONS

Short-term, intermittent nitroglycerin patch therapy significantly reduces myocardial ischemia, particularly in patients with large ischemic perfusion defects. Thallium-201 tomography can be used to assess sequential changes in the extent of exercise-induced left ventricular ischemia.

Influence of glyceryl trinitrate on venous and arterial effects of chronic, asymmetric isosorbide dinitrate treatment in patients with ischemic heart disease

Asymmetric dosage regimes have been introduced to circumvent development of nitrate tolerance. This study assessed invasively the hemodynamics during supine rest and exercise before and after 4 weeks treatment with 30 mg isosorbide dinitrate (ISDN) or placebo asymmetrically b.i.d. in 14 randomized patients with stable ischemic heart disease in a double-blinded study. An intravenous infusion of glyceryl trinitrate (GTN) was used to assess possible nitrate tolerance. During the initial, medication-free exercise all patients had increased pulmonary arterial wedge pressure (PAWP) 31.4 +/- 5.56 mmHg (mean +/- SD), showing impaired left ventricular function, while mean arterial pressures (MAP) rose from 112 +/- 16.3 mmHg at rest to 141 +/- 15.9 mmHg during exercise. After 4 weeks ISDN treatment, mean exercise PAWP and MAP, 3 h after morning dose, were reduced to 22.4 +/- 7.09 mmHg and 127 +/- 18.2 mmHg, respectively. Before the ISDN treatment, GTN reduced exercise PAWP to 13.9 +/- 5.27 mmHg and MAP to 119 +/- 11.2 mmHg, whereas after 4 weeks ISDN treatment, the addition of GTN did not reduce exercise PAWP and MAP to the same low levels. Thus, the applied ISDN regimen improved the hemodynamics, but induced a definite, partial nitrate tolerance.

Enhanced effectiveness of combined sustained-release forms of isosorbide dinitrate and diltiazem for stable angina pectoris

In 14 patients with documented coronary artery disease, the extent and duration of acute anti-ischemic, antianginal and hemodynamic effects of monotherapies with 120 mg of sustained-release isosorbide dinitrate and diltiazem were compared; their combined therapy administered once daily in the morning with diltiazem given again in the evening were also compared according to a randomized, double-blind, crossover, placebo-controlled protocol including exercise testing for assessment of ST-segment depression (ST decreases) at an identical work load, exercise capacity and determination of plasma concentrations of both substances. Comparison of individual substances revealed more marked and sustained effects of isosorbide dinitrate (ST decreases at 2 hours, -66%; at 6 hours, -50%; p less than or equal to 0.05 for both), remaining statistically significant up to 12 hours (-24%) than of diltiazem (2 hours, -30%; 6 hours, -16%; p less than 0.05). Combined therapy resulted in increased effects (ST decreases at 2 hours, -80%; 6 hours, -76%; 12 hours, -30%; p less than or equal to 0.05) as opposed to individual substances for a period of up to 12 hours. However, therapeutic coverage over 24 hours could not be demonstrated, even with renewed administration of sustained-release diltiazem in the evening. Plasma concentrations of isosorbide-5-mononitrate were greater than 250 ng/ml for 12 hours on days when isosorbide dinitrate was given, decreasing to less than 100 ng/ml at 24 hours. On days when diltiazem was given, plasma levels greater than 50 ng/ml were detected only at 2 and at 6 hours, and at 24 hours only after a second tablet was given.

Nitrates: why and how should they be used today? Current status of the clinical usefulness of nitroglycerin, isosorbide dinitrate and isosorbide-5-mononitrate

Nitrates are highly effective both in terminating acute attacks of angina pectoris and in the prophylaxis of symptomatic and asymptomatic myocardial ischemia. Preload reduction by venodilatation is the prevailing mechanism of nitrates in patients with chronic stable angina and is the unique feature distinguishing them from beta and calcium-channel blockers. Nitrates dilate coronary arteries not only in pre- and poststenotic vessels, but also in eccentric lesions. In patients with endothelial dysfunction, nitrates seem to be the physiological substitute for endothelium-derived relaxing factor. During the past decade, however, there has been substantial evidence of a clinically relevant loss of the anti-ischemic effects ("nitrate tolerance"). Many studies with oral dosing of isosorbide dinitrate or isosorbide-5-mononitrate at least three times daily have proven nitrate tolerance in patients with coronary artery disease and/or congestive heart failure. Complete loss of anti-ischemic effects after repetitive, continuous patch attachments has also been found. As we first showed in 1983, intermittent therapy with once-daily ingestion of high-dose sustained-release isosorbide dinitrate was successful in preventing the development of tolerance. Similarly, tolerance to isosorbide-5-mononitrate also does not develop when it is ingested once daily. It is now generally accepted that a daily low-nitrate interval is required to prevent tolerance development. Although the minimal patch-free interval required to prevent tolerance needs further investigation, a 12-h patch-free interval should prevent tolerance in most patients. The prolonged duration of action of once-daily high-dosage administration of sustained-release formulations, the improved patient compliance with a single daily administration, and the increased likelihood of maximal anti-ischemic effects are important reasons for recommending high single daily doses of isosorbide dinitrate or isosorbide-5-mononitrate.