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Biomedical subjects

P Kligfield

Publications and source records attributed to P Kligfield.

At least 19 recordsLinked to original sources
PubMed1992

Electrocardiographic detection of left ventricular hypertrophy by the simple QRS voltage-duration product.

OBJECTIVES: The object of this study was to assess the hypothesis that the product of QRS voltage and duration, as an approximation of the time-voltage integral of the QRS complex, can improve the electrocardiographic (ECG) identification of left ventricular hypertrophy. BACKGROUND: Electrocardiographic identification of left ventricular hypertrophy has been limited by the poor sensitivity of standard voltage criteria. However, increases in left ventricular mass can be more closely related to increases in the time-voltage integral of the summed left ventricular dipole than to changes in voltage or QRS duration alone. METHODS: Antemortem ECGs were compared with left ventricular mass at autopsy in 220 patients. There were 95 patients with left ventricular hypertrophy, defined by left ventricular mass index > 118 g/m2 in men and > 104 g/m2 in women. The voltage-duration product was calculated as the product of QRS duration and Cornell voltage (Cornell product) and the 12-lead sum of QRS voltage (12-lead product). RESULTS: At partitions with a matched specificity of 95%, each voltage-duration product significantly improved sensitivity for the detection of left ventricular hypertrophy when compared with simple voltage criteria alone (Cornell product 51% [48 of 95] vs. Cornell voltage 36% [34 of 95], p < 0.005 and 12-lead product 45% [43 of 95] vs. 12-lead voltage 31% [30 of 95], p < 0.001). Sensitivity of both the Cornell product and 12-lead product was significantly greater than that found for QRS duration alone (28%, 27 of 95, p < 0.005) and the Romhilt-Estes point score (27%, 26 of 95, p < 0.005), and compared favorably with the sensitivity of the complex Cornell multivariate score (44%, 42 of 95, p = NS). Comparison of receiver operating characteristic curves demonstrated that improved performance of the voltage-duration products for the detection of left ventricular hypertrophy was independent of test partition selection. In addition, test performance of the voltage-duration products was not significantly affected by the presence or absence of a bundle branch block. CONCLUSIONS: These data suggest that the simple product of either Cornell or 12-lead voltage and QRS duration can identify left ventricular hypertrophy more accurately than can voltage or QRS duration criteria alone and may approach or exceed the performance of more complex multiple regression analyses.

Bundle-Branch Block↗
PubMed1992

Left ventricular hypertrophy in black and white hypertensives. Standard electrocardiographic criteria overestimate racial differences in prevalence.

OBJECTIVE: To assess racial differences in the accuracy of standard electrocardiographic (ECG) criteria in the diagnosis of left ventricular hypertrophy (LVH). DESIGN: The sensitivity and specificity of standard ECG criteria were compared in blacks and whites using echocardiographic LVH as the reference standard. SETTING: Eight worksite-based hypertension clinics in New York, NY. PATIENTS: A sample of 122 black and 148 white hypertensive patients. RESULTS: The prevalence of ECG-LVH was two to six times higher in blacks than in whites, depending on the criteria used (range, 6% to 24% in blacks vs 1% to 7% in whites; P = .0005 to .19 for black-white comparisons). The difference in prevalence of echocardiographic LVH [corrected], however, was less striking and did not attain statistical significance (26% in blacks and 20% in whites; P greater than .2). The sensitivity of the ECG was low (range, 3% to 17%) and did not differ significantly between the two races for any of the conventional criteria; specificity, however, was lower in blacks for all criteria (range, 73% to 94% vs 95% to 100% for whites; P = .0001 to .09). The predictive value of a positive ECG was consistently, although not significantly, lower in the black subjects. Black race was the strongest independent predictor of decreased ECG specificity in multiple logistic regression analysis that also considered age, gender, body mass index, left ventricular mass index, and smoking. CONCLUSIONS: Commonly used ECG criteria for the detection of LVH have a poor sensitivity in both black and white hypertensives and a lower specificity in blacks than in whites; this may lead to a greater number of false-positive diagnoses in black patients, as well as to an overestimation of black-white difference in LVH prevalence.

Black People↗
PubMed1992

Identifying coronary artery disease in women by heart rate adjustment of ST-segment depression and improved performance of linear regression over simple averaging method with comparison to standard criteria.

Performance of exercise electrocardiography for the detection of coronary artery disease (CAD) in women has been limited by relatively poor sensitivity and specificity of standard test criteria. Recent studies suggest that diagnostic methods incorporating heart rate (HR) adjustment of ST-segment depression during exercise may improve the accuracy of exercise testing in women, but the relative performance of different rate-adjusted methods for this purpose is unknown. To assess the effect of gender on relative test performance of the ST-segment/HR (ST/HR) slope, the simple ST/HR index, the HR-recovery loop, and standard ST-depression criteria for the identification of CAD, the exercise electrocardiograms of 254 patients with known or suspected CAD (67 women and 187 men) and of 150 clinically normal subjects (29 women and 121 men) were analyzed. Specificity of each method was comparable in men and women: ST/HR slope 98% (118 of 121) vs 97% (28 of 29), ST/HR index 97% (117 of 121) vs 97% (28 of 29), and HR-recovery loop 96% (116 of 121) vs 93% (27 of 29). In contrast, although there was no difference in sensitivity of the ST/HR slope (95% [177 of 187] vs 93% [62 of 67]; p = not significant [NS]) or HR-recovery loop (90% [168 of 187] vs 87% [58 of 67]; p = NS) between men and women, the ST/HR index was less sensitive for CAD in women than in men (82% [55 of 67] vs 93% [173 of 187]; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Effect of measurement interval on performance of the ST integral for the identification of three-vessel coronary disease.

Measurement of the ST integral has usually incorporated ST-segment depression integrated between the J point and 80 ms after the J point (J + 80). To assess the effect of varied onset and offset of ST measurement on performance of the ST integral for the identification of three-vessel coronary disease, the exercise electrocardiograms (ECGs) of 60 patients with angiographically proven coronary disease were analyzed using J point or J + 20 onsets and J + 60 or J + 80 offsets of ST integral calculation. Simple ST-segment depression of greater than 200 microV, measured at 60 ms after the J point, identified three-vessel disease with a specificity of 68% (17 out of 25 patients) and sensitivity of 69% (22 out of 35 patients). At a matched specificity of 68% (17 out of 25 patients), there was identical sensitivity (54%, 19 out of 35 patients) of ST integrals measured either from the J point to J + 80, from the J point to J + 60, or from J + 20 to J + 60. A trend toward increased sensitivity (60%, 21 out of 35 patients) when the ST integral was measured from J + 20 to J + 80 did not reach statistical significance, and comparison of receive operating characteristics (ROC) curves demonstrated that varying the onset and offset of ST-segment measurement had no significant effect on the overall performance of ST integral criteria for the detection of three-vessel disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1992

High-frequency analysis of the signal-averaged ECG. Correlation with left ventricular mass in rabbits.

Standard electrocardiographic (ECG) criteria have exhibited poor correlation with left ventricular mass and poor sensitivity for left ventricular hypertrophy at acceptable levels of specificity. To assess the ability of the high-frequency filtered signal-averaged ECG to improve ECG correlation with left ventricular mass, signal-averaged orthogonal lead recordings in 29 normal rabbits and seven rabbits with left ventricular hypertrophy due to chronic aortic regurgitation were compared with left ventricular mass corrected for body weight. Voltage of the vector QRS complex was integrated over the total duration of the QRS after separate filtering with standard frequency (0-100 Hz) low-pass and high-frequency (44 Hz) high-pass filters. Measurement of individual X, Y, and Z lead R and S wave voltage was performed on averaged, standard frequency filtered complexes, and the maximal spatial vector magnitude was determined from the standard frequency filtered vectors. Voltage of the 44 Hz high-pass filtered vector QRS complex integrated over the total duration of the QRS (high-frequency vector integral) correlated closely with indexed left ventricular mass (r = 0.84, p less than 0.0001), significantly better than the correlation of standard frequency vector integral or maximal spatial vector magnitude voltages (r = 0.35 and r = 0.61, each p less than 0.01 vs high-frequency vector integral) and the correlation of orthogonal lead X R wave or lead Y S wave voltages (r = 0.55 and r = 0.37, respectively, each p less than 0.01 vs high-frequency vector integral).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effect of precision of ST-segment measurement on identification and quantification of coronary artery disease by the ST/HR index.

To assess the effect of varying precision of ST-segment depression measurement on test performance of the ST-segment/heart rate (ST/HR) index for the identification and quantification of coronary artery disease, the exercise electrocardiograms (ECGs) of 100 clinically normal subjects and 154 patients with angiographically proved coronary disease were reviewed. The ST/HR index was calculated by dividing the maximal additional ST-segment depression at end exercise by the exercise-induced change in heart rate. ST-segment depression was measured to the nearest 10 microV (ST10) at a point 60 ms after the J point on a computerized exercise ECG system, and was subsequently rounded down to the nearest 50 microV (ST50) and the nearest 100 microV (ST100) to simulate measurements to these precisions. An ST10/HR index partition of 1.60 microV/bpm with a specificity of 95% (95/100) in normal subjects identified the presence of coronary disease with a sensitivity of 94% (144/154). Precision of ST-segment measurement significantly affected sensitivity for coronary disease. At matched specificity of 95%, an ST50/HR index partition of 1.55 microV/bpm had a sensitivity of 88% (135/154, p less than 0.01) and an ST100/HR index partition of 1.22 microV/bpm had a sensitivity of 84% (130/154, p less than 0.001) for the detection of coronary obstructions. Comparison of receiver-operating characteristic curves (ROC) confirmed the superior overall performance of the ST/HR index using ST10 measurements for the identification of coronary disease. By contrast, test performance for the identification of three-vessel coronary disease was not affected by the precision of ST-segment measurement with no significant difference in test sensitivity or areas under respective ROCs.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Catheterization↗
PubMed1991

Heart rate adjustment of the time-voltage ST segment integral: identification of coronary disease and relation to standard and heart rate-adjusted ST segment depression criteria.

To assess the effect of heart rate adjustment of the magnitude of the ST integral (ST-HR integral) on exercise test performance, the exercise electrocardiogram (ECG) of 50 clinically normal subjects and 100 patients with known or suspected coronary artery disease was analyzed. At matched specificity of 96% with standard ECG criteria (greater than or equal to 0.1 mV of additional horizontal or downsloping ST segment depression), an unadjusted ST integral partition of 16 microV-s identified coronary disease in the 100 patients with known or suspected disease with a sensitivity of only 41%, a value significantly lower than the 59% sensitivity of standard ECG criteria (p less than 0.01) and the 65% sensitivity of an ST depression partition of 130 microV (p less than 0.001). However, test performance of the ST integral was greatly improved by simple heart rate adjustment: at a matched specificity of 96%, an ST-HR integral partition of 0.154 microV-s/beat per min identified coronary disease in the 100 patients with a sensitivity of 90%, a value significantly greater than the 59% sensitivity of standard criteria and 65% sensitivity of ST depression criteria (each p less than 0.001) and similar to the 91% sensitivity of the ST-HR index and 93% sensitivity of the ST-HR slope (each p = NS). Comparison of receiver-operating characteristic curves confirmed the superior overall test performance of the ST-HR integral relative to the ST integral and ST segment depression, and demonstrated improved performance that was comparable with that of the ST-HR index and the ST-HR slope.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

A generalized description of Wenckebach behavior with analysis of determinants of ventricular cycle-length variation during ambulatory electrocardiography.

Although variation in ventricular cycle length during Wenckebach-type second-degree atrioventricular block traditionally has been explained by the direction of incremental change in PR lengthening preceding the blocked complex, changing PP intervals can also affect Wenckebach periodicity. A generalized algebraic solution was derived to define changing ventricular cycle length as a function of both changing PP and changing incremental PR interval behavior in Wenckebach block. Based on this solution, the determinants of cycle-length variation were examined for 65 episodes of Wenckebach block detected by ambulatory electrocardiography in 51 patients. As previously demonstrated, only 20% (13 of 65) of Wenckebach episodes were characterized by the "classic" shortening of RR intervals; in contrast, ventricular cycle length increased in 57% (37 of 65) and remained constant in 23% (15 of 65) of cases. Algebraic analysis of these episodes revealed that the direction of ventricular cycle-length change preceding the blocked complex was primarily determined by the direction of change of incremental PR intervals in only 35% (23 of 65) of Wenckebach episodes; RR change was governed by the direction of change of preceding PP intervals in 34% (22 of 65) and by equal change of PP and incremental PR intervals in 31% (20 of 65) of these episodes. Both inverse and concordant relationships between changing RP and PR intervals were primarily determined by the direction of PP variation during in vivo Wenckebach block. These data confirm that classic Wenckebach block is less common than "atypical" Wenckebach periodicity and demonstrate that RR variation in Wenckebach block is governed by the changing PP interval as often as by the changing incremental PR interval.

Electrocardiography, Ambulatory↗
PubMed1991

Heart rate adjustment of exercise-induced ST segment depression. Improved risk stratification in the Framingham Offspring Study.

BACKGROUND: Simple heart rate adjustment of ST segment depression during exercise (delta ST/HR index) and the pattern of ST depression as a function of heart rate during exercise and recovery (the rate-recovery loop) have been shown to improve the ability of the exercise electrocardiogram to detect the presence of coronary heart disease (CHD), but the performance of these methods for the prediction of future coronary events remains to be examined. METHODS AND RESULTS: We compared the delta ST/HR index and the rate-recovery loop with standard electrocardiographic criteria for prediction of CHD events in 3,168 asymptomatic men and women in the Framingham Offspring Study who underwent treadmill exercise electrocardiography and who, at entry, were free of clinical and electrocardiographic evidence of CHD. After a mean follow-up of 4.3 years, there were 65 new CHD events: four sudden deaths, 24 new myocardial infarctions, and 37 incident cases of angina pectoris. When a Cox proportional hazards model with adjustment for age and sex was used, a positive exercise electrocardiogram by standard criteria (greater than or equal to 0.1 mV horizontal or downsloping ST segment depression) was not predictive of new CHD events (chi 2 = 0.40, p = 0.52). In contrast, stratification according to the presence or absence of a positive delta ST/HR index (greater than or equal to 1.6 microV/beat/min) and a positive (counterclockwise) rate-recovery loop was associated with CHD event risk (chi 2 = 9.45, p less than 0.01) and separated subjects into three groups with varying risks of coronary events: high risk, when both tests were positive (relative risk 3.6; 95% confidence interval, 2.4-5.4); intermediate risk, when either the delta ST/HR index or the rate-recovery loop was positive (relative risk, 1.9; 95% confidence interval, 1.3-2.8); and low risk, when both tests were negative. After multivariate adjustment for age, sex, smoking, total cholesterol level, fasting glucose level, diastolic blood pressure, and electrocardiographic evidence of left ventricular hypertrophy, the combined delta ST/HR index and rate-recovery loop criteria remained predictive of coronary events (chi 2 = 5.45, p = 0.02). CONCLUSIONS: Heart rate adjustment of ST segment depression by the delta ST/HR index and the rate-recovery loop during exercise electrocardiography can improve prediction of future coronary events in asymptomatic men and women.

Adult↗
PubMed1991

Effect of ST segment measurement point on performance of standard and heart rate-adjusted ST segment criteria for the identification of coronary artery disease.

BACKGROUND: Recent reports critical of the performance of heart rate-adjusted indexes of ST depression during exercise electrocardiography have used J-point rather than ST segment measurements. However, no standard exists for the optimal time after the J-point at which to measure ST segment deviation. METHODS AND RESULTS: To assess the effect of ST segment measurement position on performance of standard exercise electrocardiographic criteria, the delta ST segment/heart rate (delta ST/HR) index, and the ST segment/heart rate (ST/HR) slope for the detection of coronary artery disease, the exercise electrocardiograms of 50 clinically normal subjects and 80 patients with known or likely coronary disease were analyzed using ST depression measured at both the J-point and at 60 msec after the J-point (J + 60). A positive exercise electrocardiogram by standard criteria, defined as 0.1 mV or more of additional horizontal or downsloping ST depression at end exercise, had a specificity of 96% when ST depression was measured at either the J-point or J + 60. There was no difference in sensitivity of standard electrocardiographic criteria at J + 60 and J point (both 59%, p = NS). However, at matched specificity of 96%, the delta ST/HR index and ST/HR slope calculated using ST depression at J + 60 were significantly more sensitive (90% and 93%) than when calculated using J-point depression (64% and 61%, each p less than 0.001). Comparison of areas under respective receiver operating characteristic curves confirmed the superior performance of J + 60 as opposed to J-point measurements for both the delta ST/HR index (0.98 versus 0.89, p = 0.006) and the ST/HR slope (0.96 versus 0.87, p = 0.007) and also demonstrated modestly improved overall test performance for standard electrocardiographic criteria using J + 60 measurements (0.88 versus 0.82, p = 0.001). CONCLUSIONS: Use of J-point measurements significantly degrades performance of heart rate-adjusted indexes of ST depression but has less effect on standard criteria.

Angina Pectoris↗
PubMed1991

Natural history of left ventricular performance at rest and during exercise after aortic valve replacement for aortic regurgitation.

Previous studies of left ventricular performance in aortic regurgitation uniformly indicate improvement within the year after aortic valve replacement but differ regarding the likelihood of additional later improvement. To resolve this difference, to more precisely define the pattern of postoperative left ventricular performance variation, and to assess the impact of valve replacement on ejection fraction during exercise, we evaluated radionuclide cineangiograms obtained annually or nearly annually for approximately 5 years in 21 prospectively studied patients who had undergone valve replacement for aortic regurgitation. Ejection fraction rose from less than 8 months before operation to 5-11 (average 7) months after operation and continued to rise for 1 additional year (rest) and 2 additional years (exercise) before reaching a stable plateau until the final study 54-72 (average 63) months postoperatively. Mean ejection fractions at rest were 45% preoperatively, 50% less than 1 year postoperatively (p = 0.12), 54% at year 1-2 (p = 0.01 versus less than 1 year), 56% at year 2-3 (NS versus year 1-2) and year 4-6 (NS versus year 1-2 or 2-3), and during exercise were 39% preoperatively, 49% less than 1 year postoperatively (p less than 0.01), 54% at year 1-2 (p less than 0.01 versus less than 1 year, NS versus year 2-3, p less than 0.05 versus year 4-6), 60% at year 2-3, and 61% at year 4-6 (NS versus year 2-3). Late improvement was found most consistently among patients with relatively depressed performance before operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗