Diagnostic value of vectorcardiogram in strictly posterior infarction

Comparison of cardiogoniometry and ECG at rest versus myocardial perfusion scintigraphy

BACKGROUND

Cardiogoniometry (CGM) is a novel resting electrocardiac method based on computer-generated three-dimensional data derived from cardiac potentials. The purpose of this study was to determine CGM's and electrocardiography's (ECG) accuracy for detecting myocardial ischemia and/or lesions in comparison with stress/rest myocardial perfusion scintigraphy (single photon emission computer tomography [SPECT]).

METHOD

A cohort of consecutively enrolled patients (n = 100) with suspected or known coronary artery disease (mean age 67.8 years, 52% female) were examined by CGM and resting ECG before stress/rest myocardial scintigraphy.

RESULTS

Pathological scintigraphy findings at adenosine stress perfusion (ASP) and/or rest were conclusively identified in 21 patients. Diagnostic sensitivity was 71% for CGM and 24% for ECG, specificity was 70% for CGM and 95% for ECG. Reversible ischemia was diagnosed in 16 of 21 patients with pathological scintigraphy results. In this subgroup, sensitivity was 67% for CGM and 25% for ECG.

CONCLUSIONS

At rest, the sensitivity of a CGM significantly surmounts that of a standard 12-lead ECG for detection of isolated myocardial ischemia or myocardial lesions revealed by scintigraphy/SPECT; specificity is in a reasonable range. CGM's ease of use and its considerable agreement with the results of myocardial scintigraphy, suggests a possible role for patient screening in the primary care setting.

Electrocardiologic and related methods of non-invasive detection and risk stratification in myocardial ischemia: state of the art and perspectives

Background: Electrocardiographic methods still provide the bulk of cardiovascular diagnostics. Cardiac ischemia is associated with typical alterations in cardiac biosignals that have to be measured, analyzed by mathematical algorithms and allegorized for further clinical diagnostics. The fast growing fields of biomedical engineering and applied sciences are intensely focused on generating new approaches to cardiac biosignal analysis for diagnosis and risk stratification in myocardial ischemia.

Objectives: To present and review the state of the art in and new approaches to electrocardiologic methods for non-invasive detection and risk stratification in coronary artery disease (CAD) and myocardial ischemia; secondarily, to explore the future perspectives of these methods.

Methods: In follow-up to the Expert Discussion at the 2008 Workshop on "Biosignal Analysis" of the German Society of Biomedical Engineering in Potsdam, Germany, we comprehensively searched the pertinent literature and databases and compiled the results into this review. Then, we categorized the state-of-the-art methods and selected new approaches based on their applications in detection and risk stratification of myocardial ischemia. Finally, we compared the pros and cons of the methods and explored their future potentials for cardiology.

Results: Resting ECG, particularly suited for detecting ST-elevation myocardial infarctions, and exercise ECG, for the diagnosis of stable CAD, are state-of-the-art methods. New exercise-free methods for detecting stable CAD include cardiogoniometry (CGM); methods for detecting acute coronary syndrome without ST elevation are Body Surface Potential Mapping, functional imaging and CGM. Heart rate variability and blood pressure variability analyses, microvolt T-wave alternans and signal-averaged ECG mainly serve in detecting and stratifying the risk for lethal arrythmias in patients with myocardial ischemia or previous myocardial infarctions. Telemedicine and ambient-assisted living support the electrocardiological monitoring of at-risk patients.

Conclusions: There are many promising methods for the exercise-free, non-invasive detection of CAD and myocardial ischemia in the stable and acute phases. In the coming years, these new methods will help enhance state-of-the-art procedures in routine diagnostics. The future can expect that equally novel methods for risk stratification and telemedicine will transition into clinical routine.

Cardiogoniometric parameters for detection of coronary artery disease at rest as a function of stenosis localization and distribution

Cardiogoniometry (CGM), a spatiotemporal electrocardiologic 5-lead method with automated analysis, may be useful in primary healthcare for detecting coronary artery disease (CAD) at rest. Our aim was to systematically develop a stenosis-specific parameter set for global CAD detection. In 793 consecutively admitted patients with presumed non-acute CAD, CGM data were collected prior to elective coronary angiography and analyzed retrospectively. 658 patients fulfilled the inclusion criteria, 405 had CAD verified by coronary angiography; the 253 patients with normal coronary angiograms served as the non-CAD controls. Study patients--matched for age, BMI, and gender--were angiographically assigned to 8 stenosis-specific CAD categories or to the controls. One CGM parameter possessing significance (P < .05) and the best diagnostic accuracy was matched to one CAD category. The area under the ROC curve was .80 (global CAD versus controls). A set containing 8 stenosis-specific CGM parameters described variability of R vectors and R-T angles, spatial position and potential distribution of R/T vectors, and ST/T segment alterations. Our parameter set systematically combines CAD categories into an algorithm that detects CAD globally. Prospective validation in clinical studies is ongoing.

A system for simultaneous esophageal atrial pacing and ventricular recording in computer analysis of posterior ischemia

Abnormalities of the posterior cardiac wall are often small and obscured by electrical activity of the anterior wall of the left ventricle or by right ventricular hypertrophy. The posterior wall is hidden from the precordial leads by the anterior wall, and electrodes placed on the back are of little use because of their distance from the heart and of the intervening high-resistivity lungs. In contrast to the body surface, the esophagus provides a unique perspective of the posterior aspects of the heart at close range. The authors employed a noninvasive approach to produce cardiac stress and simultaneously record posterior cardiac electrical activity via the esophagus. A new esophageal electrode and instrumentation were developed for acquiring a high-quality esophageal electrocardiogram (ECG) during transesophageal atrial pacing stress. They present their technique for combining stress testing and computer analysis of ST-segment changes in the esophageal ECG as well as preliminary results from one normal subject and one patient with known posteroinferior ischemia.

The tall R wave in lead V1 in posterior myocardial infarction: a reciprocal sign or a His-Purkinje conduction disturbance?

The significance of the tall R wave in lead V1 with an R/S ratio greater than or equal to 1 in posterior myocardial infarction (PMI) was investigated in 28 patients during programmed electrical stimulation. The patients had been admitted with acute PMI documented by electrocardiogram and proven by enzymatic increase. Electrophysiological study was performed 3 weeks after acute PMI. In 17 of the 28 patients (group 1), the tall R wave in V1 disappeared during stimulation: In 13 of them a premature atrial extrastimulus was responsible for an abrupt normalization of QRS complex in V1 related to an increase in AH or HV interval. In the 4 remaining patients the disappearance of the tall R wave in V1 was related to a sinus pause. In 14 patients of group 1, a different prematurity in atrial stimulation induced a right or left bundle branch block (BBB). In 11 of the 28 patients (group 2) the tall R wave in V1 was unchanged but a premature atrial extrastimulus induced a right BBB in 5 patients and a left BBB in 6. In conclusion, the normalization of QRS complex in lead V1 during atrial stimulation or alterations in cycle length suggests that the tall R wave in V1 in PMI is not a simple reciprocal sign of leads V8 V9. Its association with different varieties of BBB and changes in AH or HV intervals could suggest a relationship with a His-Purkinje conduction disturbance in some patients.

Electrocardiographic and vectorcardiographic diagnosis of posterior wall myocardial infarction. Significance of the T wave

The electrocardiographic diagnosis of posterior wall myocardial infarction remains elusive. To determine discriminating criteria a group of 27 patients with posterior infarction proven by biplane angiocardiography were compared to 97 controls. All patients had single-vessel obstruction of the circumflex artery or one of its major branches (greater than or equal to 75 percent area stenosis) without occlusive disease in the other coronary arteries. High-frequency, high-gain electrocardiograms and Cube and McFee vectorcardiograms were analyzed. Pathologic Q waves in the inferior leads were present in only 22 percent (six) of the patients; increased R-wave amplitude or duration in the right precordial leads was found in 17 to 26 percent, and an R/S ratio greater than or equal to I in lead V1 or greater than or equal to 1.5 in lead V2 was present in 22 percent (six) of patients. Vectorcardiographic criteria which improved the diagnostic yield were: (1) the presence of a QRS loop mostly anterior to the E point, and (2) the presence of an abnormally anterior T wave. This abnormal T-wave shift was present in over 70 percent of the patients with posterior infarctions and was clearly discernible from the 12-lead ECG, as manifested by tall T waves in lead V2 and flat T waves in lead V6. To approximate the T-wave angle in the 12-lead scalar ECG, an index was calculated by subtracting the amplitude of the T wave in lead V6 from its amplitude in lead V2 (T2-T6 index). An index of 0.38 mV or more yielded a sensitivity of 81 percent and a specificity of 75 percent; however, this was not as discriminating as the vectorcardiogram where a T angle of 60 degrees or more in the horizontal plane yielded a sensitivity of 70 percent and a specificity of 97 percent.

Vectorcardiographic features of acute right ventricular infarction

A total of seven patients with acute inferior or inferior-posterior transmural myocardial infarction who had cardiac scintigraphically confirmed right ventricular (RV) involvement was studied. Series of vectorcardiographic tracings were taken using the Frank lead reference system from the second day after onset of acute symptoms; we found that in patients with acute inferior and RV infarction, the magnitude of the planar ST vector was greater than or equal to 0.15 mV and the projection of the ST vector pointed either to the right-anterior or right-posterior direction in the horizontal (H) plane. The serial spatial ST vector changed its direction either: 1) from right-anterior-inferior octant to right-posterior-inferior octant or vice versa; or 2) from right-posterior-inferior octant to right-anterior-superior octant. The larger the magnitude of the rightward ST vector, especially right-anterior direction in the H plane, the greater the probability of acute RV infarction. In patients with acute inferior-posterior and RV infarction, the magnitude of the ST vector in the H plane was greater than or equal to 0.2 mV. The spatial ST vector pointed to the right-posterior-inferior octant and its direction did not change from the original octant in the serial tracings during the course of the acute stage. Our data suggest that vectorcardiography--a non-invasive, non-nuclear polluting, and economical method--has shown great potential to become, in the near future, the primary non-invasive diagnostic test of choice for acute RV infarction.

[Pattern quantification of coronary artery stenosis by computerized analysis of multiple ECG parameters (author's transl)]

Coronary angiograms of 200 patients with coronary artery disease were studied. The distribution of stenoses was analyzed and classified utilizing a special score, taking into account coronary supply pattern (according to Baroldi et al.), localization and severity of stenosis, as well as collateralization. Frank-lead vectorcardiograms were obtained and analyzed by computer. 140 scalar and spatial vector parameters were evaluated. A statistical comparison was made in 36 patients with highgrade stenoses of the left anterior descending branch of the left coronary artery with 37 patients without such vascular narrowing. Utilizing 4 ECG-parameters a mathematical formula can be derived which separates the two groups. Another equation based on 5 parameters allows the calculation of a score from conventional electrocardiograms. By discriminance analysis a specificity of 78.4% and a sensibility of 77.8 in prediction results for the group with stenosis. For the control group a specificity of 75.7% and a sensibility of 77.8% were computed. Correlation between the score obtained by calculation on the one hand, and the score derived from direct analysis of the arteriogram was highly significant with an r = 0.796.

Differentiation of posterior myocardial infarction from right ventricular hypertrophy and normal anterior loop by echocardiography

The differentiation of posterobasal myocardial infarction (PMI) from either right ventricular hypertrophy (RVH) or normal subjects displaying an anterior loop (AL) by electrocardiography (ECG) or vectorcardiography (VCG) is difficult. M-mode echocardiography (echo) via the anterior and subxiphoid methods has been helpful in defining cardiac chamber size and wall motion abnormalities. We tested whether this relatively more direct method would better separate these entities compared with the other two techniques. ECG and VCG using established criteria failed to distinguish the three conditions effectively. By echo, distinguishing characteristics were observed in each of the groups. Thus, right ventricular diastolic dimension and wall thickness were significantly increased only in the RVH group, echo dimensions and wall motion were normal in the AL group and the posterior left ventricular systolic thickening response and ejection phase indices were significantly reduced only by the subxiphoid method in the PMI group. To test the specificity of the latter finding, posterior wall motion in three infarction groups (posterior, combined posteroinferior and inferior) were examined and suggested that the target of the subxiphoid beam focuses on a more superior posterobasal left ventricular segment than the anteriorly placed transducer. Echocardiography can differentiate PMI from either RVH or AL more directly than ECG or VCG, and may be of practical clinical importance.

Relation of angina to coronary artery disease in mitral and in aortic valve disease

Of 129 patients with either mitral or aortic valve disease angina was present in 55 (42%). It was more frequent in aortic (60%) than in mitral valve disease (33%). The standard 12-lead electrocardiogram was not helpful in distinguishing underlying occlusive coronary artery disease. Coronary arteriography demonstrated coronary artery disease in 26 patients (20%), only 2 of whom had no angina. The incidence of coronary artery disease was almost identical in both the mitral and aortic groups (22% and 17%, respectively), but the percentage of those with demonstrable coronary artery disease accompanying angina was much higher in the mitral group (67% as against 29%). Angina in mitral valve disorders is thus much more likely to be the result of disease of the coronary arteries. Coronary arteriography is mandatory in all patients in both groups who have angina. Otherwise it seems unnecessary as coronary artery disease was found in only 2 patients who did not have angina.

Vectorcardiographic criteria of high posterior infarction: differentiation from normal subjects, right ventricular hypertrophy and primary myocardial disease

In order to differentiate the vectorcardiogram (VCG) in high posterior infarction (HPI) from VCGs of normal subjects, right ventricular hypertrophy (RVH) and primary myocardial disease (PMD), the following criteria were presented; cases satisfying the criteria could be diagnosed as high posterior infarction. In cases with posterior component/anterior component (P/L) less than 1.0 (Group A); (1)--45 degrees vector/ab less than or equal to 0.25, (2) the maximal T vector in the horizontal plane greater than or equal to + 20 degrees, (3) I (inferior component)/L (left component) less than 1.0 and (4) no anterior convexity of the afferent limb of the left sagittal QRS loop. In cases with P/A greater than or equal to 1.0 (Group B);--45 degrees vector/ab less than or equal to 0.2, (2) the maximal T vector in the horizontal plane greater than or equal to + 20 degrees, (3) I/L less than 1.0 and (4) no anterior convexity of the affernt limb of the left sagittal QRS loop. Only one false negative case in HPI was found and only seven false positive cases in normal subjects, RVH and PMD. A correct diagnosis can be made with 97.4% accuracy. These criteria for differentiation were tested by reexamining the cases with selective coronary arteriography. Five cases satisfied the criteria of this method. Complete obstruction of the circumflex coronary artery was found in four of these cases, and severe stenosis (greater than or equal to 90%) in one case. Akinesis or hypokinesis of the posterobasal segment in the left ventricle was also observed in all five cases.

Advances in clinical vectorcardiography

With use of the Frank lead system, still loop and timed vectorcardiograms were recorded in more than 5,000 patients sujected to complete right and left hear catheterization and selective coronary cine angiography. Data so obtianed demonstrated clincila superiority of the vectorcardiogram over the standard 12 lead scalar electrocardiogram. Specific advantages of the vectorcardiogram include (1) recognititin of undetected atrial and ventrcular hypertropy, (2) greater sensitivity in identification of myocardial infaraction, and (3) superior capability for diagnosis of multiple infaractions in the presnece of fascicular and burnany number of simultaneously recoreded electrocardiographic leadsfor the analysis of complex arrhythmias and beat to beat changes in intraventricula conduction. SINCE THE VALIDITY AND USEFULNESS OF THIS TECHNIQUE HAVE BEEN ESTABLISHED, IT SHOULD BECOME PART OF THE ROUTINE NONINVASIVE EVALUATION OF PATIENTS WITH CARDIOVASCULAR DISORDERS.