Left axis deviation: diagnostic contribution of exercise stress testing

Transient left posterior hemiblock during myocardial ischemia-eliciting exercise treadmill testing: a report of a case and a critical analysis of the literature

We describe a 75-year-old male patient with two-vessel coronary artery disease, who developed transient left posterior hemiblock (LPH) while undergoing an exercise treadmill test (ETT). The intraventricular conduction abnormality initially had the features of alternating LPH, which evolved to stable LPH prior to dissipating, and it occurred at the first minute of recovery. The exercise electrocardiogram and the associated thallium-201 myocardial perfusion scintigraphy (Tl) revealed severe reversible myocardial ischemia. This rare occurrence is discussed in the context of the observed coronary lesions, the distribution of the radionuclide-detected ischemia, and the previous experience from the literature. An insight regarding the low prevalence of transient LPH is afforded, since the described case derives from a series of 2,160 consecutive patients who underwent ETT in conjunction with Tl. Finally, a comment is provided on the complexities of deciphering the specific pathophysiologic mechanism(s) of transient LPH, occurring during ETT.

Accuracy of exercise electrocardiography in detecting physiologically significant coronary arterial lesions

The accuracy of exercise electrocardiography in detecting a physiologically significant coronary artery stenosis has been assessed previously by comparing the exercise test with a coronary arteriogram. The inherent inaccuracy of visually determined percent diameter stenosis measurements might have lead to the conclusion that the exercise electrocardiogram was less accurate than it truly was. To determine the accuracy of the exercise electrocardiography in detecting a physiologically significant coronary stenosis, we studied 40 patients with one-vessel, one-lesion coronary artery disease, a normal resting electrocardiogram, and no hypertrophy or prior infarction. Each patient underwent exercise electrocardiography (Bruce protocol) that was interpreted as abnormal if the ST segment developed 0.1-mV or greater depression 80 msec after the J point. The physiological significance of each coronary stenosis was assessed by measuring of coronary flow reserve (peak divided by resting blood flow velocity) in the stenotic artery using a Doppler catheter and intracoronary papaverine (normal, 3.5 or greater peak/resting velocity). The percent diameter and percent area stenosis produced by each lesion were determined using quantitative angiography (Brown/Dodge method). Of the 17 patients with reduced coronary flow reserve (3.5 or greater peak/resting blood flow velocity) in the stenotic artery, 14 had an abnormal exercise electrocardiogram (sensitivity, 0.82; 95% confidence interval, 0.70-0.94). Conversely, 20 of 23 patients with normal coronary flow reserves had normal exercise tests (specificity, 0.87; 95% confidence interval, 0.77-0.97). The exercise electrocardiogram was abnormal in each of 11 patients with markedly reduced coronary flow reserve (less than 2.5 peak/resting velocity) and in three of six patients with moderately reduced reserve (2.5-3.4 peak/resting velocity). The products of systolic blood pressure and heart rate at peak exercise were significantly correlated with coronary reserve in patients with truly abnormal exercise tests. In comparison, the sensitivity (0.61; 95% confidence interval, 0.46-0.76) and specificity (0.73; 95% confidence interval, 0.60-0.86) of exercise electrocardiography in detecting a 60% or greater diameter stenosis may be significantly lower (p less than 0.05). Exercise electrocardiography, therefore, was a good predictor of the physiological significance (assessed by coronary flow reserve) of a coronary stenosis in patients with a normal resting electrocardiogram and no hypertrophy or prior infarction. Its value in a broader and larger patient population will require further study. These results, however, underscore the importance of a physiological gold standard in assessing the accuracy of noninvasive studies for detecting coronary artery disease.

Left anterior fascicular block: an ischaemic response during treadmill testing

A patient in whom exercise induced reversible ischaemic left anterior fascicular block is reported. Glyceryl trinitrate relieved the fascicular block. Coronary angiography showed a 90% obstruction of the left anterior descending artery. The left anterior fascicular block induced by exercise disappeared after a successful coronary angioplasty.

Characteristics and prognosis of incomplete right bundle branch block: an epidemiologic study

A cohort of 1,960 white men aged 40 to 56 years without initial apparent heart disease and with 11 years of annual rest electrocardiograms and 20 year mortality data was followed in the Chicago Western Electric Company Study. Incomplete right bundle branch block was found in 134 men (6.8%) at entry. During follow-up, 222 men developed such block, an incidence rate of 13.6%. Left axis deviation of -30 degrees or less was more frequent in men with than in those without incomplete block at entry (8.2 versus 2.4%). Men with left axis deviation also had a higher incidence of incomplete right bundle branch block. Similarly, men developing incomplete block had a significantly greater risk of developing left axis deviation. The associations between incomplete block and left axis deviation were unrelated to age and body weight. Men with incomplete block had a significantly greater likelihood of developing complete right bundle branch block. The 11 year incidence rate of complete block was 5.1% for men with baseline incomplete block and 0.7% for those without. Complete block developed in 2 of 220 incident cases of incomplete block but in none of the 440 control men matched by age and duration of follow-up. Although incomplete right bundle branch block was not related to an increased risk of death in 20 years from coronary heart disease and cardiovascular diseases, the study data suggest that such block is frequently a manifestation of primary abnormality of the cardiac conduction system in middle-aged men.

Ischemia-associated intraventricular conduction disturbances during exercise testing as a predictor of proximal left anterior descending coronary artery disease

To determine the incidence and significance of transient intraventricular conduction abnormalities occurring in association with myocardial ischemia during exercise testing, the recordings of 2,200 consecutive exercise tests were reviewed. Ten patients (0.45%) were identified as having both ischemia and intraventricular conduction abnormalities that developed transiently during the exercise test. In all 10 patients both typical angina and electrocardiographic evidence of ischemia developed during exercise. Among the 10 patients, left anterior hemiblock developed in 4, left posterior hemiblock in 2, right bundle branch block (RBBB) in 2, RBBB with left axis deviation in 1, and left anterior hemiblock progressing to complete left bundle branch block (LBBB) in 1. All 10 patients had cardiac catheterization showing significant obstruction of the left anterior descending (LAD) coronary artery at or before the origin of the first septal branch. Eight patients were treated surgically and 2 medically, all with relief of ischemic symptoms. Nine of the 10 had repeat exercise stress testing without angina or electrocardiographic evidence of ischemia and without recurrence of the transient intraventricular conduction disturbance. It is concluded that the development of transient intraventricular conduction abnormalities associated with myocardial ischemia during exercise testing is an uncommon occurrence (0.45%). When such conduction disturbances do develop, the existence of significant disease in the proximal portion of the LAD coronary artery is strongly suggested. With control of myocardial ischemia, the transient conduction disturbances during exercise are ameliorated.

Left axis deviation: diagnostic contribution of stress testing and post-exercise systolic time intervals

The response to graded submaximal upright bicycle ergometry combined with resting and postexercise systolic time intervals (STIs) was investigated in ten ambulatory subjects (study group) with normal electrocardiograms except for a frontal plane axis of greater than or equal to -30 degrees, or left axis deviation (LAD) mean -40 degrees); and eight age-matched volunteers (control group) with a normal ECG and frontal plane axis (mean +35 degrees). Following a 12-lead resting ECG, supine STIs were measured. The subjects then exercised on a bicycle ergometer at progressive workloads with ECG and blood pressure monitoring until a heart rate based on 85 percent of tha age-predicted maximum was attained or an abnormal end point was noted. STIs were repeated immediately postexercise. Prolongation of left ventricular ejection time corrected for heart rate (LVETc) of 8 msecs or more from rest to post-exercise. (deltaLVETc) was considered an abnormal STI response. The deltaLVETc can elicit left ventricular dysfunction and possible latent organic heart disease in patients with isolated left axis deviation.

Left-axis deviation: etiologic factors in one-hundred patients

Clinical and electrocardiographic findings were analyzed in 100 consecutive cases of LAD. Below the age of forty years, LAD was uncommon, but its incidence increased continuously thereafter. The most frequent primary clinical diagnosis was arteriosclerotic heart disease. The functional mechanism producing LAD most often was LAHB, responsible in about 40 per cent. Approximately half the instances of LAHB were associated with old myocardial infarction of septal, anterior, or lateral regions, but half were seen in the absence of infarction or clinical coronary sclerosis and are presumed due to primary degenerative processes within these specialized conducting fibers. Approximately one-sixth of the instances of LAD were due to loss of inferior forces following inferior myocardial infarction. Typical left ventricular hypertrophy was a distinctly uncommon cause of LAD. Last, in 24 patients with LAD the mechanism or cause was not evident initially, of which two were subsequently shown to represent a very mild degree of LAHB. Also it is suggested that asymmetric myocardial hypertrophy of the anterior wall may account for some instances of LAD not otherwise explained.