A basic approach to the interpretation of the exercise test

To interpret the exercise test, the following parameters need to be evaluated: the heart rate and blood pressure response, symptoms, dysrhythmias, aerobic capacity, and evidence for myocardial ischemia. When analyzing the ST segment for ischemia, the amount and type of ST depression and the time of onset and resolution are examined. The exercise test results are best used to determine a post-test probability that the patient has significant coronary disease, predict its severity, and provide a prognosis of the patient. The test allows primary care physicians to decide which patients with coronary artery disease can be safely managed medically and which high-risk patients need further evaluation and consideration for revascularization.

The utility of four biochemical markers in the triage of chest pain patients

Four biochemical markers, creatine kinase (CK)-MB isoenzyme, myoglobin, myosin light chains and troponin I, were studied in 1,338 patients presenting to the emergency department with chest pain suggestive of coronary artery disease (CAD). One hundred and eighty-seven patients had an acute myocardial infarction (MI). At least one of the four markers was over the threshold on the first sample in 78% of MI patients, as compared to only 40% with an elevated CK-MB. After 4 h, 88% had at least one marker elevated. None of the 69 patients with atypical chest pain, no history of CAD, no markers over threshold on the first sample and a normal electrocardiogram had an acute MI or unstable angina. If we had discharged this group, we would have saved USD 264,000, estimating a cost of USD 2,000 per day. Using four biochemical markers improved the early diagnosis of CAD and may help identify groups suitable for early discharge.

The time has come to reexamine the gold standard when evaluating noninvasive testing

Angiographically identified 50% cross-sectional narrowing of a coronary artery fails to accurately identify compromised myocardial perfusion. Noninvasive tests should be correlated with intravascular ultrasound or coronary flow reserve to determine their clinical utility.

Underuse and overuse of diagnostic testing for coronary artery disease in patients presenting with new-onset chest pain

PURPOSE

To determine the extent of overuse and underuse of diagnostic testing for coronary artery disease and whether the socioeconomic status, health insurance, gender, and race/ethnicity of a patient influences the use of diagnostic tests.

SUBJECTS AND METHODS

We identified patients who presented with new-onset chest pain not due to myocardial infarction at one of five Los Angeles-area hospital emergency departments between October 1994 and April 1996. Explicit criteria for diagnostic testing were developed using the RAND/University of California, Los Angeles, expert panel method. They were applied to data collected by medical record review and patient questionnaire.

RESULTS

Of the 356 patients, 181 met necessity criteria for diagnostic cardiac testing. Of these, 40 (22%) failed to receive necessary tests. Only 7 (3%) of the 215 patients who received some form of cardiac testing had tests that were judged to be inappropriate. Underuse was significantly more common in patients with only a high school education (30% vs 15% for those with some college, P = 0.02) and those without health insurance (34% vs 15% of insured patients, P = 0.01). In a multivariate logistic regression model, only the lack of a post-high school education was a significant predictor of underuse (odds ratio 2.2, 95% confidence interval 1.0 to 4.4).

CONCLUSION

Among patients with new-onset chest pain, underuse of diagnostic testing for coronary artery disease was much more common than overuse. Underuse was primarily associated with lower levels of patient education.

Significance of ST-segment depression with R-wave amplitude decrease on exercise testing

A retrospective evaluation was performed of patients who underwent exercise tests and angiography and 50 ambulatory normal subjects who underwent only exercise testing. We found that when deltaST depression of 0.5 mm was combined with deltaR-wave decrease of 1 mm, the sensitivity and specificity were improved.

Hyperbaric oxygen and thrombolysis in myocardial infarction: the 'HOT MI' randomized multicenter study

In a previous pilot study, we demonstrated that adjunctive treatment with hyperbaric oxygen (HBO) appears to be feasible and safe in patients with acute myocardial infarction (AMI) and may result in an attenuated rise in creatine phosphokinase (CPK), more rapid resolution of pain and ST changes. This randomized multicenter trial was organized to further assess the safety and feasibility of this treatment in human subjects. Patients with an AMI treated with recombinant tissue plasminogen activator (rTPA) or streptokinase (STK), were randomized to treatment with HBO combined with either rTPA or STK, or rTPA or STK alone. An analysis included 112 patients, 66 of whom had inferior AMIs (p = NS). The remainder of the patients had anterior AMIs. The mean CPK at 12 and 24 h was reduced in the HBO patients by approximately 7.5% (p = NS). Time to pain relief was shorter in the HBO group. There were 2 deaths in the control and 1 in those treated with HBO. The left ventricle ejection fraction (LVEF) on discharge was 51.7% in the HBO group as compared to 48.4% in the controls (p = NS). The LVEF of the controls was 43.4 as compared to 47.6 for those treated, approximately 10% better (no significant difference). Treatment with HBO in combination with thrombolysis appears to be feasible and safe for patients with AMI and may result in an attenuated CPK rise, more rapid resolution of pain and improved ejection fractions. More studies are needed to assess the benefits of this treatment.

Detecting exercise-induced ischemia in left bundle branch block using the electrocardiogram

We compared 12-lead electrocardiographic changes during exercise in 41 patients with left bundle branch block; 7 were nonischemic and 34 had coronary artery obstruction > or =70% as detected by angiogram. ST depression of > or =0.5 mm from baseline when measured at the J point in leads II and AVF (p=0.004) and an increase of R-wave amplitude in lead II (p=0.05) significantly identified ischemia.

Hyperbaric oxygen and thrombolysis in myocardial infarction: the "HOT MI" pilot study

Hyperbaric oxygen treatment (HBO) in combination with thrombolysis has been demonstrated to salvage myocardium in acute myocardial infarction in the animal model. Therefore a randomized pilot trial was undertaken to assess the safety and feasibility of this treatment in human beings. Patients with an acute myocardial infarction (AMI) who received recombinant tissue plasminogen activator (rTPA) were randomized to treatment with HBO combined with rTPA or rTPA alone. Sixty-six patients were included for analysis. Forty-three patients had inferior AMIs (difference not significant) and the remainder had anterior AMIs. The mean creatine phosphokinase level at 12 and 24 hours was reduced in the patients given HBO by approximately 35% (p = 0.03). Time to pain relief and ST segment resolution was shorter in the group given HBO. There were two deaths in the control group and none in those treated with HBO. The ejection fraction on discharge was 52.4% in the group given HBO compared with 47.3% in the control group (difference not significant). Adjunctive treatment with HBO appears to be a feasible and safe treatment for AMI and may result in an attenuated rise in creatine phosphokinase levels and more rapid resolution of pain and ST segment changes.

Time course of changes in P-wave duration during exercise

The exercise-induced increase in P-wave duration reported previously has not been studied on a minute-by-minute basis. We measured the P duration in 47 normal subjects and 43 coronary artery disease (CAD) patients each minute during an exercise test. We found that prolongation of the P wave in those with CAD occurs relatively early and the difference between normal subjects and CAD patients is greater near maximum exercise. The data suggest that an increase in P-wave duration may reflect an increase in the left-ventricular end-diastolic pressure and may occur earlier that ST-segment depression.

Electrocardiographic evidence of ischemia during ventricular paced rhythms

Exercise-induced electrocardiographic (ECG) changes are the most widely recognized noninvasive means for detecting myocardial ischemia. The specificity of these changes depends on the normalcy of the resting ECG. Right ventricular pacing produces major QRS and ST-T changes very similar to those of complete left bundle-branch block. They alter the resting ECG such that ischemic changes are considerably difficult to detect. Because of these resting abnormalities, ECG changes during treadmill exercise testing usually do not facilitate the diagnosis of ischemia or coronary artery disease. The following are two cases of ischemic ECG changes that occurred during right ventricular pacing. To our knowledge, there have been no reports of the classic ECG changes of ST-segment depression suggestive of ischemia which occurred during right ventricular pacing and which were discernible from the resting ECG changes.

Significance of precordial T-wave increase during treadmill stress testing

It appears that a T-wave amplitude increase of > or = 2.5 mm in lead V2 during a treadmill stress test may be specific (95%), even though this finding only occurs occasionally. Therefore, a T-wave amplitude increase during an exercise test may aid in the diagnosis of the few patients who develop this abnormality, especially if there is no ST depression, as has occurred during several recent exercise tests.

A basic approach to the interpretation of the exercise test

For primary care physicians, exercise testing is a cost-effective tool to evaluate patients presenting with symptoms. It helps to stratify those with probable coronary artery disease into a high-risk group needing referral and a low-risk group that can be observed. Each of the five main responses--the presence of myocardial ischemia, the heart rate and blood pressure response, the symptoms, any dysrhythmias, and the maximal aerobic capacity--should be mentioned in the final report. A suggested format for the exercise test report is shown in Table 4. Using the tools of pretest and post-test probability, the severity of disease, and the exercise treadmill scores greatly aids the primary care physician in the management of the patient evaluated with an exercise test.

Diagnostic accuracy of predicting coronary artery disease related to patients' characteristics

Patients' demographic and clinical characteristics may affect diagnostic accuracy of cardiologists. We asked a group of experienced cardiologists from three institutions to estimate the pretest probability of coronary artery disease in 257 patients referred for diagnostic coronary angiography and with no history of previous myocardial infarction nor valvular heart disease. Physicians pretest estimates were compared with the diagnostic findings of coronary angiography. We tested the influence of five variables on the accuracy of the pretest estimates: age, sex, chest pain characteristics, rest electrocardiogram and electrocardiographic exercise test result. Cardiologists tended to overestimate the presence of coronary artery disease and this tendency was particularly remarkable in the group of patients showing a negative exercise test. Pretest diagnostic accuracy was 0.72 when the test result was negative and 0.85 when the test result was positive (95% confidence interval of the difference 0.03 to 0.23; p < 0.001). The diagnosis of coronary artery disease was also more accurate for male than for female patients (0.81 vs 0.70; 95% confidence interval of the difference 0.02 to 0.21; p < 0.02). Characteristics of chest pain, age and rest electrocardiogram did not affect the level of pretest diagnostic accuracy. Cardiologists should be cognizant of correctly interpreting a negative exercise test and the clinical data of female patients; in both cases, they should move circumspect of the diagnosis of coronary artery disease.

Exercise testing in special situations

This article discusses exercise testing in valvular heart disease, hypertension, and the evaluation of patients for surgery. It also provides information on the effects of drugs on the exercise test and the clinical significance of block patterns and arrhythmias encountered during exercise.

Computer probability estimates of angiographic coronary artery disease: transportability and comparison with cardiologists' estimates

A computer algorithm for estimating probabilities of any significant coronary obstruction and triple vessel/left main obstructions was derived, validated, and compared with the assessments of cardiac clinician angiographers. The algorithm performed at least as well as the clinicians when the latter knew the identity of the patients whose angiograms they had decided to perform. The clinicians were more accurate when they did not know the identity of the subjects but worked from tabulated objective data. Referral and value induced bias may affect physician judgment in assessing disease probability. Application of computer aids or consultation with cardiologists not directly involved with patient management may assist in more rational assessments and decision making.

Analysis of the signal-averaged P-wave duration in patients with percutaneous coronary angioplasty-induced myocardial ischemia

To assess the impact of angioplasty-induced myocardial ischemia on the duration of the surface P wave, patients undergoing elective angioplasty of isolated lesion in the left anterior descending, circumflex or right coronary arteries were monitored with a 3-channel electrocardiographic Holter system. The leads used were modified bipolar chest leads V5, aVF and V2 (CM-V5, CS-aVF and CM-V2). After echocardiographic signal-averaging, the earliest onset and the latest offset of the P wave were identified in all of the above time-aligned signal-averaged leads, and the composite maximal P duration was measured under 10 x magnification. The maximal ST-segment shift during balloon inflation was also measured in all of the above leads at 60 ms after the J point. In the study group comprising 47 patients, the mean signal-averaged P-wave duration was 125.0 +/- 16 ms at baseline versus 130.0 +/- 15 ms during balloon inflation, p less than 0.005. In the left anterior descending coronary artery group (n = 23), the mean signal-averaged P-wave duration was 122.4 +/- 17 ms and 131.3 +/- 16 ms during balloon inflation, p less than 0.005). In the group with a right coronary artery lesion (n = 18), the values were 127.3 +/- 14 ms and 128.4 +/- 13 ms respectively (p = not significant). Significant increases in the P-wave duration were found to occur in groups both with (n = 34) and without (n = 13) ST-segment shift greater than or equal to 1 mm (both p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical assessment of the probability of coronary artery disease: judgmental bias from personal knowledge

Probability estimates of angiographic coronary artery disease made by experienced, board-certified staff cardiologists were compared with those of cardiologists in training (fellows). In addition, estimates made before coronary angiography were compared with those made several months later based on written clinical summaries of 15 items of objective clinical and test data. Cardiologists were asked to estimate the probabilities of coronary artery disease, multivessel disease, and triple-vessel or left main disease. The study population consisted of 510 consecutive patients without valvular disease referred for the first time for coronary angiography to three hospitals. Both staff and fellows consistently overestimated the pre-angiographic probability of coronary artery disease. The probabilities estimated from patient summaries were always significantly lower than the pre-angiographic assessments. Only staff cardiologists reliably assessed the probabilities of coronary artery disease during the second assessment (p less than 0.05). Thus, estimates of disease probability based on clinical judgment vary according to the source of information, and these estimates are more accurate when physicians have objective data on hand and do not know the identities of the patients.

The predictive value of the time course of ST segment depression during exercise testing in patients referred for coronary angiograms

We studied the time course of ST segment depression during and after exercise testing in 462 subjects who also had coronary angiograms. Sixty-three percent of patients with late onset-early offset ST depression, previously reported to be likely to have false positive tests, had significant coronary artery disease, and 32% had three-vessel disease. Those with early onset and late offset ST depression and those with resting ST depression that was accentuated with exercise had a high prevalence of significant coronary artery disease and three-vessel disease. We found that observation of the time course of ST depression during and after exercise adds significantly to the information gained during exercise testing.

Efficacy of three-channel ambulatory electrocardiographic monitoring for the detection of myocardial ischemia

The recognition of silent myocardial ischemia (SMI) has been demonstrated to have important clinical relevance. Two-channel ambulatory (Holter) electrocardiographic recording is a commonly utilized method for detecting transient electrocardiographic ST segment changes representative of SMI. It has been suggested that the analysis of two channels alone may not adequately detect SMI. We therefore evaluated the diagnostic yield of three channels using a three-channel electrocardiographic monitoring device in 46 consecutive patients (age 61 +/- 9 years) undergoing percutaneous transluminal coronary angioplasty of an isolated single-vessel stenosis. Modified bipolar chest leads V2, V5, and AVF (CM-V2, CM-V5, and CS-AVF) were utilized for analysis. The percent detection of ST segment changes from various combinations of two-lead recordings were compared to the total three leads, and an absolute transient ST segment shift (STSS) of greater than or equal to 1 mm during balloon inflation was considered as evidence of myocardial ischemia. One patient was excluded because of the need for ventricular pacing during balloon inflation. A total of 33 of 45 patients had STSS in all three leads (percent detection = 73%), while 32 (71%) had STSS in the two-lead grouping with the highest diagnostic yield (CM-V2/CM-V5; p = ns). Of the various two-lead combinations studied, leads CM-V2 and CM-V5 provided the best lead set overall for the detection of ischemic STSS. Three-channel ambulatory electrocardiographic recording only marginally improves upon the detection of ischemia when compared with standard (CM-V2/CM-V5 or CM-V5/CS-AVF) two-channel ambulatory electrocardiographic recordings.

The significance of lead strength on ST changes during treadmill stress tests

The contribution of relative lead strengths to ST depression during exercise was evaluated in 334 patients who had both a treadmill stress test and an angiogram. Patients were referred for exercise testing for the evaluation of suspected or known coronary artery disease. This was accomplished by comparing the magnitude of ST-segment depression to a constructed ST/R ratio. Using a cutoff of 0.1 for the ST/R ratio, the data were compared to the sensitivity and specificity of the 1 mm criteria for ST depression. There was only a slight increase in sensitivity (59% vs 63%) and specificity (60% vs 78%) for the ST/R ratio in comparison to the standard ST depression. However, when these two criteria were reevaluated for patients with less than or equal to 10.0 mm of R wave amplitude, the 0.1 ST/R ratio had a small decrease in specificity (94% vs 80%) when compared to 1 mm of ST depression and a marked increase in sensitivity with 31% for the standard ST depression and 82% using the ST/R ratio. In those with an R wave greater than 20 mm, 1 mm of ST depression was much more sensitive than the ST/HR ratio (95% vs 59%), but the ratio was more specific than the conventional ST depression (78% vs 59%). It is concluded that ST depression should be corrected for R wave amplitude in patients with R waves less than 10 mm and over 20 mm.

Significance of signal-averaged P-wave changes during exercise in patients with coronary artery disease and correlation with angiographic findings

The maximal P-wave duration in all time-aligned leads, and the maximal P-wave amplitude in leads V5 and V6 were measured on a 12-lead, signal-averaged electrocardiogram during the recovery period of an exercise stress test (EST). The study group consisted of 75 patients with coronary artery disease (CAD) documented by greater than or equal to 50% diameter stenosis in 1 or more arteries and a control group of 47 subjects, 15 of them young volunteers and 32 with no or minimal coronary atherosclerosis and normal left ventricular function. All subjects underwent a symptom limited EST, with use of the Ellestad protocol. Signal-averaged P waves recorded before exercise, and for the first 6 minutes in recovery were measured using a 5x magnifier. The mean P duration before exercise in the control group was 107 +/- 16 ms (+/- 1 standard deviation) and 111 +/- 15 ms at the third minute of recovery, (p less than 0.001). In patients with CAD it was 112 +/- 12 and 129 +/- 19 ms (+/- 1 standard deviation), p less than 0.001, respectively. Differences in P-wave duration were found to be statistically significant (p less than 0.001) throughout recovery in the group with CAD when compared with control and maximal values at the third minute. The increase in P-wave duration (greater than or equal to 20 ms) was used as an additional parameter to exercise-induced ST-segment depression, ST elevation, or anginal pain for the test interpretation. The sensitivity increased from 57 to 75% and the specificity decreased from 85 to 77%.(ABSTRACT TRUNCATED AT 250 WORDS)

Dacron-woven pacemaker pouch. Influence on long-term pacemaker mobility

Pacemaker migration can interfere with correct pacing system function and patient comfort. A Dacron pouch has been developed which may prevent these problems. To assess the efficacy of the pouch, we measured various factors of pacemaker mobility in 100 patients after long-term follow-up. The patients were divided into three groups on the basis of their dictated operative reports: group 1, no pouch or anchoring stitch; group 2, pouch only; group 3, anchoring stitch to pacemaker header or pouch. The average age of the study population was 74.3 +/- 11 years. Total follow-up time was 42 +/- 28 months (group I, 53 +/- 32 months; group 2, 36 +/- 23 months; group 3, 34 +/- 25 months). There were no significant differences when pacemakers were measured for movement in the inferosuperior and lateromedial directions, nor was there any difference in the distance between the incision scar and the pacemaker header in any group. There was a significant difference between group 1 and groups 2 and 3 when the degree of tilt of the pacemaker off the chest wall was compared. This was 46 degrees +/- 34 degrees for group 1 and 27 degrees +/- 26 degrees and 26 degrees +/- 27 degrees for groups 2 and 3, respectively (p less than 0.02 for both). These data suggest that the Dacron pouch does not restrict pacemaker mobility parallel to the chest wall during long-term follow-up but does reduce the angle to which the pacemaker can be tilted relative to the chest wall.

Impaired activity rate responsiveness of an atrial activity-triggered pacemaker: the role of differential atrial sensing in its prevention

The physiological benefit of rate responsive, single-chamber cardiac pacing is well documented. We studied the activity response of nine atrially placed Activitrax II pacemakers. Seven patients were noted to have an inadequate activity-rate response with maximal pacing rates of 85 to 101 beats/min. Marker Channel analysis revealed that the upper rate timeout was reset by far-field R wave sensing, even when sensing occurred in the atrial refractory period. These 9 pacemakers were tested by atrial sensitivity adjustment for ability to exclude far-field R wave sensing, while preserving P wave sensing. Unipolar implantation data were then examined for predictors of this differential far-R and P-wave sensing. Differential atrial sensing occurred in 4/9 pacemakers (2/2 bipolar in the right atrial appendage; 0/1 bipolar in the coronary sinus; and 4/9 unipolar). An empirically developed index utilizing unipolar implant parameters discriminated outcomes for 8/9 unipolar pacemakers. We conclude that: (1) the rate responsiveness of the atrial Activitrax II pacemaker is limited by far-field R wave sensing even when this occurs during atrial channel refractoriness; (2) reprogramming atrial sensitivity to differentially sensed P and far-field R waves may restore appropriate rate responsiveness; and (3) although a unipolar implant discriminant index may correctly identify adequacy of future rate responsiveness, the atrial application of the Activitrax II pacemaker is cautioned until further validation is forthcoming, particularly when used in unipolar and coronary sinus applications.

Iliac vein approach to permanent pacemaker implantation

Since July 1980, 90 patients have had 95 permanent pacemakers implanted via an iliac vein approach. An incision is made superior to the inguinal ligament and the iliac vein is cannulated with a single lead for the ventricle or two leads for the atrium and ventricle. The pulse generator is placed in the subcutaneous tissue of the abdomen lateral to the umbilicus via a second incision. Overall 28 pacemaker implants were for atrial pacing, 53 for ventricular pacing and 14 were dual chamber. Nine (21%) of the atrial leads displaced and required repositioning and 5 (7%) of the ventricular leads dislodged and required revision. Lead dislodgement, especially in the atrium, remains a major weakness of the approach, and decreases its utility. Eleven percent of the last 19 atrial leads have dislodged. Nevertheless, the method is simple to perform and is presented as an alternative to the usual pectoral implantation site.

Experiences with atrial pacing

The records of 187 patients with permanent atrial pacemakers implanted between 1970 and 1980 were studied retrospectively to define the indications, outcome and short- and long-term complications of single-chamber atrial pacing. Pacemakers were implanted in 145 (77%) patients with tachybrady syndrome, 35 (19%) with sinus bradycardia and 7 (4%) with ventricular arrhythmia. Intact atrioventricular (AV) conduction was defined as absence of second- or third-degree heart block with incremental atrial pacing to a heart rate of 120 beats/min before implantation. The average follow-up was 30 months, including 87 patients (46%) who were followed an average of 48 months. Four patients developed significant conduction disease requiring placement of a ventricular lead. Complications included 4 lead fractures (all coronary sinus leads), 10 dislodgments (9 coronary sinus, 1 tined atrial "J") and 6 threshold rises requiring repositioning of the lead. Eight dislodgments occurred within an average of 5.6 days. The average increase in threshold that required repositioning occurred at 14 days. The average lead fracture occurred at 25 months. Atrial pacing is safe and effective for patients with sinoatrial node disorder (sick sinus syndrome) and intact AV conduction. Progression to clinically significant AV block is uncommon. Complications occur early with coronary sinus leads and are less common with newer leads.

Autonomic responses in chest pain syndromes as compared to normal subjects

The heart rate response to standing, cough, hand grip, and deep breathing were examined in normal subjects and coronary artery disease patients (greater than 70% diameter narrowing). The heart rate responses to these maneuvers were reduced in coronary patients and in anginal patients with normal coronary angiograms, as compared to normals. Detection (with the heart rate response to standing) was determined by using an RR interval cutoff of 140 ms for males and 120 ms for females discriminated between normals and CAD patients. In men sensitivity was 0.58, specificity 0.87 and CCR 0.75, and in women sensitivity was 0.67, specificity 0.79 and CCR 0.75. These values are similar to those reported for ST segment depression in similar populations. When separating normals from those with 2 and 3 vessel disease--sensitivity is 0.67, specificity 0.87, predictive value 0.71 and CCR 0.80. The response to cough, hand grip, and deep breathing showed similar trends but had less specificity than the response to standing. Thus, the heart rate response to most autonomic maneuvers is blunted in subjects with coronary disease and in those with pain syndromes sent for coronary angiography. These findings need testing in larger populations but autonomic maneuvers fail to discriminate patients with coronary disease from those with normal angiograms presenting with chest pain syndromes.

The cardiointegram: detection of coronary artery disease in males with chest pain and a normal resting electrocardiogram

The cardiointegram is a non-invasive technique for the analysis of the electrical signals of the heart obtained by a transformation of the voltage vs. time format by a series of integrations. This multicenter study compares the results of the cardiointegram with coronary arteriography in 140 male patients with chest pain and a normal resting electrocardiogram. The cardiointegram was determined on two resting complexes of Leads I, II, V4, V5 and V6 and called abnormal if greater than or equal to four of ten complexes were abnormal, i.e., fell outside of a previously determined template of normality. The sensitivity was 73% and specificity was 78% for the diagnosis of occlusive coronary artery disease. When greater than or equal to five of ten abnormal complexes were used as the cut-off for an abnormal test and "equivocal" results (four of ten abnormal, n = 18) were excluded from analysis there was a sensitivity of 69% and specificity of 88%. Thirty-seven of 38 patients (97%) with an abnormal cardiointegram and a positive exercise stress test had coronary artery disease. Thus, the cardiointegram appears to be a useful non-invasive test for the detection of coronary artery disease in males with chest pain and a normal resting electrocardiogram in whom the diagnosis of coronary artery disease is being considered.

Does exercise alter anaerobic threshold in coronary artery disease during beta blockade?

The effect of propranolol on cardiac patients undergoing exercise training is reported to increase exercise tolerance and maximum oxygen uptake (VO2 max) but its effect on anaerobic threshold (AT) is unknown. It was the purpose of this study to determine the role of exercise training with propranolol on AT in patients with coronary artery disease (CAD). Eight men and one woman with significant (CAD) were selected for this study. Each patient completed a maximum treadmill stress test (MTST) following the Bruce protocol on propranolol 40-160 mg/day as a control study. Cardiorespiratory variables were measured at rest and at each stage of the treadmill test. These patients underwent an exercise training programme for 12-16 weeks on the same dose of propranolol. Training sessions were for a minimum of 30-40 minutes, 3 times a week, with training heart rate of 75%-85% of the pretraining peak heart rate. Training heart rate ranged from 98 to 128 beats/min. They were retested with a MTST after the training programme, on the same dose of propranolol. AT was calculated noninvasively by measuring respiratory variables every 30 seconds in relation to work increment. AT was identified by measuring the time course of VE, VCO2, VE/VO2, etc. in relation to incremental work. The mean values of VO2, O2P and % VO2 max at AT before and after training on propanolol were as follows: VO2 = 1.43 L/min +/- .25 and 1.86 L/min +/- .44, O2P = 14.35 +/- 2.40 and 18.73 +/- 4.00 ml/beat, % of VO2 max = 68.20 +/- 6.31 and 73.59 +/- 5.84. The mean changes of VO2 O2P, and % of VO2 max were + 0.43 L/min +/- 0.20 (P < .003), + 4.38 +/- 2.55 (P < .003) and +/- 5.07% +/- 4.84 (P < .001). After exercise training on propanolol, the mean peak exercise tolerance time and absolute VO2 max increased by 2.8 min (from 9.0 to 11.8 min) (P < .001) and 22.7% (P < .007), respectively. We conclude that the increase in anaerobic threshold in patients with coronary artery disease may be due to improvement in VO2 max, increased stroke volume, and peripheral O2 extraction.

Naloxone and asymptomatic ischemia: failure to induce angina during exercise testing

Endorphins and endorphin receptors are believed to modulate pain perception. To investigate whether naloxone, a specific antagonist, could initiate anginal pain during exercise-induced myocardial ischemia in asymptomatic patients with angiographically defined coronary artery disease, a single-blind trial was conducted in 10 men with prior positive exercise electrocardiograms. Multistage treadmill exercise tests were performed twice within a week. On the second test, patients received naloxone, 2 mg intravenously, by a syringe infusion pump. Exercise was terminated because of fatigue in 6 patients and completion of the protocol in 4. No patient reported chest pain during exercise. Naloxone did not significantly alter exercise duration, heart rate, blood pressure and ST-segment changes compared with control testing. It is concluded that endorphins do not play a significant role in the recognition of anginal pain in patients who have asymptomatic exercise-induced ischemia.

Coronary artery bypass surgery morbidity

A retrospective analysis was undertaken of 365 consecutive patients, 75 women and 290 men with a mean age of 59.9 +/- 9.7 years, who had coronary artery bypass surgery during 1981. Complications classified as major were: mediastinal hemorrhage, pericardial tamponade, wound dehiscence, sternal osteomyelitis, myocardial infarction, bacterial endocarditis, dissecting aneurysm and diabetes insipidus. Complications classified as minor were: atrial fibrillation, postpericardiotomy syndrome, cellulitis, thrombophlebitis and phrenic nerve palsy. There were 48 patients (13%) with 52 major complications. Age more than 60 years, cardiopulmonary bypass time longer than 150 minutes, aortic cross-clamp time longer than 100 minutes, number of grafts greater than five and presence of diabetes mellitus were significantly associated with major complications. Complications tended to occur more frequently in women, obese patients and those with emergency operation or ejection fraction less than 30%, but the associations were not statistically significant. Physicians referring patients for coronary artery surgery should be cognizant of the incidence of morbidity along with the other risks and benefits when considering coronary artery bypass surgery.

The exercise test as a guide to management and prognosis

The exercise stress test is one of the most useful procedures available in the management of ischemic heart disease. It can provide a good deal of information, in addition to ST segment changes, for the clinician to interpret. Analysis of test results allows more accurate diagnosis, estimation of the severity of disease, and establishment of prognosis.

Status of exercise stress testing after myocardial infarction

The use and current limitations of early exercise testing of the patient with a postmyocardial infarction (MI) is reviewed. The test provides useful information in identifying patients at high risk of a second coronary event, thereby helping direct possible interventional therapy. It also furnishes information regarding the patient's capacity for physical exertion, detection of ventricular arrhythmias, and extent of coronary artery disease. Angina, ST segment responses, BP, and ventricular arrhythmias during early exercise testing are evaluated for their importance in determining prognosis. The concomitant use of thallium scintigraphy and radionuclide ventriculography seems to augment detection of multivessel disease and left-ventricular dysfunction. A practical strategy for the use of early exercise testing in the evaluation of post-Mis is provided.

Comparison of the multivariate analysis and CADENZA systems for determination of the probability of coronary artery disease

The accuracy of 2 discriminate systems for diagnosis of coronary artery disease (CAD), multivariate analysis (MVA) and Bayesian analysis (CADENZA), was evaluated in 113 patients undergoing electrocardiographic stress testing and coronary angiography. MVA uses weighting factors (F values) generated from our patient data, whereas CADENZA uses probabilities gleaned from an extensive review of the American literature. Overall accuracy was similar. MVA had a higher sensitivity for 1-vessel CAD (75 versus 33%), but CADENZA was better for determining the severity of CAD. The 2 systems provided posterior probabilities for disease that were highly correlated (r = 0.56; p less than 0.001). Both systems suggest the need for further testing based on the probability generated; herein lies their major strength. The application of such systems should help the clinician reach a diagnosis or make a decision as to management in a cost-effective manner.

Transient central diabetes insipidus after aortocoronary bypass operations

Three cases of transient central diabetes insipidus after cardiopulmonary bypass are presented. All 3 patients responded promptly to administration of vasopressin, and were completely recovered from polyuria 10 days after cardiac surgery. It is postulated that transient diabetes insipidus after cardiac operation occurred in some patients who had preexisting selective osmoreceptor dysfunction when cardiac standstill during extracorporeal circulation alters the left atrial nonosmotic receptor function, resulting in suppression of antidiuretic hormone release.