Detection of ambulatory ischaemia is not of practical clinical value in the routine management of patients with stable angina. A long-term follow-up study

[Long term electrocardiography (Holter monitoring)]

During the past almost 50 years Holter monitoring has become an established non-invasive diagnostic tool in clinical electrophysiology. It allows ECG recording independent of stationary monitoring facilities during daily life and, therefore, contains much information. In the beginning the main interest was directed towards quantitative and qualitative assessment of arrhythmias, their circadian behaviour, and the circadian behaviour of the heart rate. With advances in technology the analysis spectrum of Holter monitoring expanded, and it was used also for detection of silent myocardial ischaemia. New digital recorders and computers with large capacities made it possible to measure every single heart beat very accurately, which was a prerequisite for heart rate variability and QT-interval analysis, which provided new knowledge about the autonomic modulation of the heart rate and the circadian dynamicity of the QT interval, respectively. Beyond arrhythmia analysis Holter monitoring was increasingly used to assess prognosis in different cardiac conditions. It can also be valuable in assessing transient symptoms possibly related to arrhythmias or device dysfunction, which will not necessarily be revealed by simple device control.

The electrocardiogram as a prognostic tool for predicting major cardiac events

Among patients with cardiac disease, the identification of those who are at low risk and those who are at high risk for major cardiac events is crucial for a rational clinical management of individual patients. A correct noninvasive risk stratification of cardiac patients, in particular, has relevant clinical implications because it would avoid unnecessary exposure to potentially risky invasive diagnostic or interventional procedures in low-risk patients, whereas it would allow an appropriate aggressive diagnostic and therapeutic approach in high-risk patients. Furthermore, the appropriate identification of low- and high-risk patients would also have social and economic implications by favoring optimization of resource distribution and costs. A large number of studies in previous decades provided evidence that several methods and variables derived from the analysis of the electrocardiogram (ECG) are powerful predictors of major cardiac events in several clinical conditions. Despite that, there has been limited attention about how several of these findings can be used in clinical practice. Furthermore, in recent years, most studies about risk stratification of cardiac patients have mainly been focused on the use of a number of serum/plasma biomarkers with reduced attention to ECG variables. Surprisingly, however, there have been few attempts to establish whether the various proposed risk markers add any significant information to that obtainable from ECG methods. In this article, the evidence for the prognostic value of variables derived from the assessment of the ECG signal by several methods and techniques will be briefly reviewed. Because of the largeness of the topic, this review will be necessarily incomplete. Because most of the clinical research in this field concerned risk stratification of patients with coronary artery disease, the article will be largely focused on this population of patients. The role of ECG methods in specific cardiac diseases and, in particular, in the general population of asymptomatic subjects will be briefly discussed when believed appropriate and helpful. Furthermore, only major clinical events (ie, cardiac death, arrhythmic events, acute myocardial infarction) will be taken into account as end points in this article. Minor clinical events (eg, coronary revascularization procedures, coronary artery restenosis, recurrences of symptoms) are indeed less robust as end points because they are widely biased by subjective judgments.

Myocardial ischaemia in patients with peripheral arterial disease

AIM

To study the relation between myocardial ischemia assessed with different techniques in patients with peripheral arterial disease (PAD) in comparison with a matched control group.

METHODS

Ninety-nine male patients with PAD and 94 age- and sex-matched control subjects without PAD or ischaemic heart disease performed a exercise treadmill test, dipyridamole Tc-99m sestamibi myocardial perfusion SPECT (MPS) (43 controls) and 48-h ambulatory ECG (AECG)-monitoring (43 controls).

RESULTS

Thirteen of 99 patients had irreversible and 24 of 99 had reversible perfusion defects in MPS in comparison with 0 of 43 and six of 43 of control subjects respectively (P<0.01). Thirteen of 84 evaluable patients experienced a total of 36 episodes of ST-depression in AECG in comparison with two episodes in two of 42 control subjects (P = 0.07). Out of 13 patients with ST-depression episodes only three had reversible ischaemia in MPS.

CONCLUSION

Most PAD patients with episodes of ST-segment depression have no reversible ischaemia as assessed with dipyridamole-stress MPS. Episodes of ST-segment depression may reflect types of myocardial ischaemia that are different from those detected by MPS.

Diabetes mellitus and cardiovascular disease

Diabetes is associated with a high incidence and poor prognosis of cardiovascular disease, and with high short- and long-term mortality. Adequate treatment of cardiovascular disorders and aggressive management of coexisting risk factors have proved to be at least as effective in diabetic as in nondiabetic patients in randomized, controlled studies. Indeed, treating diabetic patients with cardiovascular disease results in a larger absolute risk reduction than in nondiabetic subjects. Nevertheless, diabetic patients often receive inadequate therapy, which may, to a certain extent, explain their poor prognosis. Recommendations for the treatment of diabetic patients with acute myocardial infarction should include beta-blockers, aspirin, and ACE-inhibitors in all patients in whom no specific contraindications exist. Fibrinolysis should be administered when indicated, and the benefits of improving glycemic control should not be forgotten either. In patients with multi-vessel disease who need revascularization, when selecting the type of procedure, the superiority of surgical revascularization over angioplasty should be borne in mind. Even heart transplantation should be included as a therapeutic option since there are no data to support the exclusion of patients on account of their diabetes. Finally, coexisting risk factors should be intensively treated through lifestyle intervention, with or without drug therapy, in order to achieve secondary prevention goals.

Prognostic implications of ambulatory myocardial ischemia and arrhythmias and relations to ischemia on exercise in chronic stable angina pectoris (the Angina Prognosis Study in Stockholm [APSIS])

The prognostic significance of ambulatory ischemia, alone and in relation to ischemia during exercise was assessed in 686 patients (475 men) with chronic stable angina pectoris taking part in the Angina Prognosis Study In Stockholm (APSIS), who had 24-hour ambulatory electrocardiographic registrations and exercise tests at baseline (n = 678) and after 1 month (n = 607) of double-blind treatment with metoprolol or verapamil. Ambulatory electrocardiograms were analyzed for ventricular premature complexes and ST-segment depression. During a median follow-up of 40 months, 29 patients died of cardiovascular (CV) causes, 27 had a nonfatal myocardial infarction, and 89 underwent revascularization. Patients with CV death had more episodes (median 5 vs. 1; p<0.01) and longer median duration (24 vs. 3 minutes; p<0.01) of ST-segment depression than patients without events. For those who had undergone revascularization, the duration was also longer (12 vs. 3 minutes; p<0.05). In a multivariate Cox model including sex, history of previous myocardial infarction, hypertension, and diabetes, the duration of ST-segment depression independently predicted CV death. When exercise testing was included, ambulatory ischemia carried additional prognostic information only among patients with ST-segment depression > or =2 mm during exercise. When the treatment given and treatment effects on ambulatory ischemia were added to the Cox model, no significant impact on prognosis was found. Ventricular premature complexes carried no prognostic information. Thus, in patients with stable angina pectoris, ischemia during ambulatory monitoring showed independent prognostic importance regarding CV death. Ambulatory electrocardiographic monitoring and exercise testing provide complementary information, but only among patients with marked ischemia during exercise. Treatment reduced ambulatory ischemia, but the short-term treatment effects did not significantly influence prognosis.

Circadian blood pressure changes and myocardial ischemia in hypertensive patients with coronary artery disease

OBJECTIVES

We sought to evaluate whether different circadian blood pressure (BP) changes could influence the occurrence of ischemic episodes in untreated and treated hypertensive patients with stable coronary artery disease (CAD).

BACKGROUND

In hypertensive patients with CAD the occurrence of myocardial ischemia could be influenced by either high or low BP values. Ambulatory monitoring has shown that circadian BP profile is not uniform in hypertensive patients.

METHODS

Twenty-one patients with a nighttime BP fall < 10% ("nondippers"), 35 with a nighttime BP fall between > 10% and < 20% ("dippers") and 14 with a nighttime BP fall > 20% ("overdippers") with CAD underwent simultaneous ambulatory BP and electrocardiographic monitoring before and during drug therapy with nitrates and atenolol or verapamil in a prospective, randomized, open, blinded end point design.

RESULTS

Daytime BP was not significantly different among the groups both before and during therapy. Nighttime BP was different by definition. Treatment significantly reduced BP values in each group (p < 0.05). Daytime ischemic episodes did not differ among the groups either before or during therapy. Drug therapy significantly reduced daytime ischemia (p < 0.05). In untreated patients, nighttime ischemia was more frequent in nondippers than in dippers and overdippers (p < 0.05). Drug therapy significantly reduced nocturnal ischemia in nondippers (p < 0.05), had no significant effect in dippers and significantly increased nighttime ischemia in overdippers (p < 0.05). During treatment, nighttime ischemia was more frequent in overdippers than in dippers and nondippers (p < 0.05). The same results were achieved when ischemic episodes were defined with more restrictive criteria (ST segment depression > or = 2 mm).

CONCLUSIONS

Circadian BP changes can influence the occurrence of myocardial ischemia in untreated and treated hypertensive patients with CAD. Nocturnal ischemia was found to be more frequent in nondippers among untreated patients and in overdippers among treated patients, potentially suggesting different therapeutic approaches based on circadian BP profile.

Amlodipine versus diltiazem as additional antianginal treatment to atenolol. Centralised European Studies in Angina Research (CESAR) Investigators

The antianginal efficacy and tolerability of amlodipine and diltiazem were compared in a double-blind randomized trial of 97 patients with angina resistant to atenolol alone. Both amlodipine and diltiazem significantly reduced the frequency of angina attacks (p <0.001) and glyceryl trinitrate consumption (p <0.05 to p <0.01). During Holter monitoring, both treatments reduced the overall frequency of ambulatory myocardial ischemia, although changes did not reach statistical significance. Exercise test parameters (total exercise time, time to angina, time to ST depression, and maximum ST depression) tended to improve with both treatments, but changes did not achieve statistical significance relative to baseline or to each other. Both drugs were generally well tolerated. Adverse events occurred in 15 patients in the amlodipine group (30%) and in 17 patients in the diltiazem group (36%), but patients taking diltiazem reported almost twice as many adverse events (30) patients taking amlodipine (18). Quality of life, as assessed by total Nottingham Health Profile Scores, was not significantly different between treatments. The addition of either once-daily amlodipine or twice-daily sustained release diltiazem improved symptoms in patients with angina resistant to atenolol alone, but diltiazem was associated with more frequent and more serious adverse events.

Natural variability of transient myocardial ischaemia during daily life: an obstacle when assessing efficacy of anti-ischaemic agents?

OBJECTIVE

To assess the degree of variability of transient myocardial ischaemia during daily life in patients with coronary artery disease, which could confound the interpretation of trials of the therapeutic effects of anti-ischaemic agents.

DESIGN

Prospective method evaluation.

SETTING

Tertiary referral centre, outpatient clinic.

PATIENTS

Patients with stable angina, confirmed coronary artery disease, and a positive treadmill exercise test for ischaemia. Patients were not preselected on the basis of prior documented transient ischaemia during ambulatory ST segment monitoring.

INTERVENTIONS

A simulated drug-study with 4 monitoring phases in 16 subjects. To minimise variability in ischaemic activity, patients underwent weekly 48 hour ambulatory ST segment monitoring outside hospital off all prophylactic therapy on the same weekdays for 4 weeks.

MAIN OUTCOME MEASURE

Variability in the frequency and duration of transient myocardial ischaemia.

RESULTS

There was marked variability in both ischaemic activity and mean duration of ischaemia in patients with confirmed ischaemia, the greatest degree of variability being between patients and from day to day within weeks within patients, with a further contribution to variability being noted between fortnights within patients.

CONCLUSIONS

Despite assessment off all therapy and an adequate period of monitoring (48 hours) with small intervals between monitoring periods (5 days), marked variability in ischaemic activity was noted, and regression towards the mean was clearly shown. Ambulatory ST segment monitoring outside hospital is not a reliable method for assessing the therapeutic effects of anti-ischaemic agents.

Tenuous link between ischaemic threshold and both ambulatory ischaemia and symptom status over time in stable angina: a 5-year follow-up study

This study evaluates changes in ischaemic threshold over a 5-year period in patients with stable angina pectoris, who did not suffer any intervening cardiac event. Changes in ischaemic threshold are related to alterations in symptomatic status and ambulatory ischaemia. Over long-term follow-up, there is a significant fall in ischaemic threshold in such patients (mean heart rate at onset of ischaemia fell from 104 +/- 17.8 to 97 +/- 17.4 bpm: P < 0.001), but this is not matched by a worsening of either symptoms or ischaemia during daily life. In the 68% of patients that had a reduction in ischaemic threshold of > or = 5 bpm, 68% had either definite reduction or no change in symptoms and 84% had either reduction, abolition or no change in transient ischaemic activity. The dissociation between ischaemic threshold, ambulatory ischaemia and symptoms has implications for long-term monitoring and management of the patient with stable angina.

Prognostic significance of transient ischemic episodes: response to treatment shows improved prognosis. Results of the Total Ischemic Burden Bisoprolol Study (TIBBs) follow-up

OBJECTIVES

The Total Ischemic Burden Bisoprolol Study (TIBBS) follow-up examined cardiac event rates in relation to transient ischemia and its treatment.

BACKGROUND

It is unclear whether transient ischemia on the ambulatory electrocardiogram has prognostic implications in stable angina and whether medical treatment can improve the prognosis.

METHODS

The TIBBS trial was an 8-week, randomized, controlled comparison of the effects of bisoprolol and nifedipine on transient ischemic episodes in patients with stable angina pectoris. Of the 545 patients screened, 520 (95.4%) could be followed up. Rates of cardiac and noncardiac death, nonfatal acute myocardial infarction, hospital admission for unstable angina and need for coronary artery bypass graft surgery or percutaneous transluminal coronary angioplasty were recorded.

RESULTS

A total of 145 events occurred in 120 (23.1%) of 520 patients. Patients with more than six episodes had an event rate of 32.5% compared with 25.0% for patients with two to six episodes and 13.2% for patients with less than two episodes (p < 0.001). Hard events (death, acute myocardial infarction, hospital admission for unstable angina pectoris) were more frequent in patients with two or more ischemic episodes (12.2% vs. 4.7%, p = 0.0049). Patients with a 100% response rate of transient ischemic episodes during the TIBBS trial had a 17.5% event rate at 1 year compared with 32.3% for non-100% responders (p = 0.008). Patients receiving bisoprolol during the TIBBS tria had a lower event rate (22.1%) at 1 year than patients randomized to nifedipine (33.1%, p = 0.033).

CONCLUSIONS

In patients with stable angina pectoris, frequent episodes of transient ischemia are a marker for an increased event rate. A 100% response to medical treatment reduces the event rate. The greater reduction of ischemia with bisoprolol than nifedipine during the TIBBS trial translated into an improved outcome at 1 year.