Daily life ischemia and nitrate therapy

Appropriateness of nitrate use in a general medicine population

BACKGROUND

Nitrates are one of the most commonly prescribed drug groups for cardiac disease, especially for angina pectoris and congestive heart failure. The chronic efficacy of nitrates is limited by the development of tolerance, which can be attenuated by use of sustained-release preparations or administration of regular-release preparations asymmetrically.

OBJECTIVE

To determine whether patients receiving isosorbide 5-mononitrate (ISMN) use the drug in a pharmacologically appropriate manner and whether they had been instructed in the prophylactic use of sublingual nitrates prior to effort.

METHODS

We administered a questionnaire regarding details of nitrate use to 229 patients with ischemic heart disease using oral ISMN, prescribed prior to their current admission. The study was conducted in a 600-bed university-affiliated hospital.

RESULTS

We found that only 15% of patients receiving regular-release ISMN were taking the drug asymmetrically. In contrast, 82.6% of the patients receiving sustained-release ISMN were using the drug properly. Only 38.1% of the patients treated with regular-release ISMN were treated with the dose recommended in the literature. Furthermore, of the 190 patients who reported experiencing effort angina, only 17.9% had been instructed in the prophylactic use of nitrates prior to effort.

CONCLUSIONS

The majority of patients (85%) using regular-release ISMN were taking the medication in an inappropriate fashion, while most patients taking sustained-release preparations were using them properly. More than half the patients treated with regular-release ISMN were treated with doses exceeding the recommended dose. In addition, most patients experiencing effort angina had not been instructed regarding the prophylactic use of nitrates. These findings suggest that both physicians and pharmacists must be reminded of the continuing need to properly counsel patients regarding appropriate drug use.

Effects of intermittent transdermal nitroglycerin on occurrence of ischemia after patch removal: results of the second transdermal intermittent dosing evaluation study (TIDES-II)

OBJECTIVES

We sought to evaluate the effects of intermittent transdermal nitroglycerin (TD-NTG) on the occurrence of ischemia during patch-off hours in patients with stable angina pectoris receiving a beta-adrenergic blocking agent or calcium antagonist, or both.

BACKGROUND

The current recommendations for the use of intermittent TD-NTG may be associated with the occurrence of rebound ischemia.

METHODS

This was a multicenter, randomized, double-blind, placebo-controlled, crossover trial with three study periods. Tolerability to TD-NTG was assessed in Period I. Seventy-two patients were assigned to receive either double-blind transdermal placebo or maximally tolerated TD-NTG for 2 weeks (Period II) and were then crossed over to the alternative treatment for another 2 weeks (Period III). The patients were instructed to apply medication daily at 8 AM, to remove it at 10 PM and to note symptoms and sublingual nitroglycerin (SL-NTG) use in a diary. The occurrence of ischemia was assessed from patient-perceived angina, symptom-limited exercise treadmill test (ETT) and 48-h ambulatory electrocardiographic (AECG) monitoring.

RESULTS

Transdermal NTG (0.2 to 0.4 mg/h) significantly reduced the magnitude of ST segment depression at angina onset during ETT compared with placebo. Total angina frequency was not significantly different between TD-NTG (mean [+/-SD] 3.2 +/- 4.2) and placebo (3.3 +/- 5.2). During patch-off hours, angina frequency increased with TD-NTG (1.1 +/- 2.1) compared with placebo (0.7 +/- 1.6) (p = 0.03). Similar trends for an increase in ischemia after TD-NTG were also observed from AECG analyses. Specifically, ischemia frequency tended to be lower during patch-off hours for placebo than with TD-NTG (0.05 +/- 0.09 vs. 0.08 +/- 0.20 episodes/h, respectively, p = 0.08), even though frequency of ischemia tended to be higher during patch-on hours for placebo than with TD-NTG (0.12 +/- 0.19 vs. 0.07 +/- 0.15 episodes/h, respectively, p = 0.11). During placebo, ischemia frequency decreased 58% (patch-on to patch-off, p = 0.01) compared with a 14% increase with TD-NTG. These changes attenuate the usual circadian variation in ischemia.

CONCLUSIONS

An increase in ischemia frequency during patch-off hours after use of intermittent TD-NTG was perceived by patients, and this subjective finding was supported by a corresponding trend for AECG ischemia to increase during these same hours.

Nitrate tolerance in angina therapy. How to avoid it

Tolerance is the attenuation, or loss, of one or several of the effects of organic nitrates after long term administration. All organic nitrate regimens using frequent doses of long-acting nitrates (3 or more times daily), continuous delivery systems [transdermal nitroglycerin (glyceryl trinitrate) patches or continuous intravenous infusions of nitroglycerin] or long-acting (sustained release) preparations will result in partial or complete nitrate tolerance. There are several proposed mechanisms which may contribute to the development of tolerance including activation of neurohormonal mechanisms, plasma volume expansion and depletion of intracellular sulfhydryl cofactors. To avoid tolerance to long term nitrate therapy, regimens should be tailored to provide a 10- to 12-hour nitrate-free interval when possible. This means that antianginal prophylaxis can only be provided by nitrate therapy for some portion of each day, and that some patients will develop an increase in angina in the nitrate-free intervals which will necessitate short term therapy with sublingual nitroglycerin or a similar preparation.

Silent myocardial ischemia

The documentation of abnormalities related to myocardial ischemia, whether symptomatic or silent, is of central importance. Whenever this information is available, it should be used in the overall assessment of the patient at risk for adverse outcome. The level of concern for treatment of CAD should be based on the risk implications associated with the ischemia-related abnormalities detected during objective testing rather than on the presence or absence of pain. The exercise stress test is still the single most useful test to begin the evaluation of a patient with an analyzable ST segment. In persons suspected of having CAD, the detection of ischemic-type ST-segment depression, at a low workload (e.g., < 120 beats/min or < 6.5 METS) of > 2 mm magnitude or persisting for more than 6 min implies high risk for adverse outcome. Asymptomatic ischemia during everyday activities, detected by Holter monitoring, in the high-risk patient, most probably adds additional risk beyond the risk of an abnormal stress test alone. Left ventricular imaging by two-dimensional echocardiography, RNA, angiogram, vest, etc, showing an ejection fraction > or = 40%, reversible wall motion abnormalities in multiple regions and redistribution defects or a failure to increase ejection fraction during exercise even if the patient remains asymptomatic, also imply high risk. The presence of any of these abnormal findings, regardless of symptoms, should therefore prompt as high a degree of concern as with ischemia-related signals associated with pain. Thus any therapy chosen should be directed toward elimination of transient ischemia, not just relief of symptoms that may or may not be ischemia related. If this course is chosen, the efficacy of the therapeutic regimen and possible progression of CAD should be assessed with follow-up testing for ischemia. We believe that risk factor modification and aspirin should be considered for most, if not all, patients in whom ischemia, silent or symptomatic, is suspected or detected. If symptoms or ischemia suggesting low risk is present, anti-ischemic medical therapy may be considered, but follow-up is advised. If a high-risk ischemic signal, even without symptoms, is detected, medical therapy should be used to attempt to modify the signal. If the ischemic signal suggesting high risk persists despite medical therapy, revascularization should be considered. Until additional data from large clinical trials are available, this approach appears to have the greatest likelihood of modifying the adverse outcome of CAD.