The electrocardiogram of myocardopathy

Imaging myocardial scar and arrhythmic risk prediction--a role for the electrocardiogram?

Risk stratification for sudden cardiac death (SCD) has become increasingly important to identify candidates for implantable cardioverter-defibrillators (ICDs). Existing clinical guidelines to identify patients for ICDs focus on reduced left ventricular ejection fraction (LVEF); however, the average annual rate of appropriate ICD shocks is only 5.1% in this select group (LVEF <or=35%), and these patients only represent a small fraction of the total number of patients who die of SCD. Magnetic resonance imaging (MRI) with late gadolinium enhancement has recently emerged as the in vivo gold standard for detecting and quantifying myocardial scar after infarction and in nonischemic cardiomyopathies. Myocardial scar, particularly in the scar border zone, interrupts electrical conduction providing regions that support reentrant ventricular arrhythmias. Recent studies have shown that increased MRI scar in both prior infarction and nonischemic cardiomyopathy patients is associated with arrhythmogenesis, worsening heart failure, and cardiac mortality. This review will focus on the emerging role of MRI to quantify scar and predict arrhythmogenesis in patients with prior infarction and with nonischemic cardiomyopathies-including idiopathic, hypertrophic, Fabry's disease, myocarditis, Chagas' disease, and sarcoidosis. Furthermore, this review will discuss the potential role of the 12-lead electrocardiographic Selvester QRS scoring system to quantify myocardial scar and predict arrhythmogenesis in prior infarct and nonischemic cardiomyopathy patients.

Premature ventricular complex morphology. A marker for left ventricular structure and function

The shape of a premature ventricular complex (PVC) might reflect the presence or absence of myocardial disease. To test this, 100 patients with a PVC on a 12-lead electrocardiogram at cardiac catheterization or nuclear angiography were classified according to PVC morphology. Group 1 (n = 50) had PVC QRS complexes with either smooth and uninterrupted contour or with narrow (less than 40 msec) notching. Group 2 (n = 50) demonstrated PVC with broad (greater than or equal to 40 msec) notching or shelves. Clinical, electrocardiographic and angiographic variables were assessed to define group differences. All patients had one or more etiological forms of heart disease none of which distinguished either group. Groups 1 and 2 differed with respect to a history of congestive heart failure (12% vs. 66%, p = 0.0004), dilated cardiomyopathy (2% vs. 38%, p = 0.0005), and the presence of mitral regurgitation (13% vs. 58%, p = 0.001), respectively. In group 1, 45 of 50 (90%) patients with a PVC had no notching. Patients in group 2 had greater PVC QRS duration as compared with patients in group 1 (181 +/- 6 vs. 134 +/- 3 msec, p = 0.0001). End-diastolic volume index (EDVI) (78 +/- 3 vs. 139 +/- 11 ml/m2, p = 0.0000) and ejection fraction (EF) (0.59 +/- 0.02 vs. 0.34 +/- 0.03, p = 0.0000) significantly discriminated between group 1 and 2, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Serial electrocardiographic changes in idiopathic dilated cardiomyopathy confirmed at necropsy

Serial electrocardiographic changes in necropsy-proven idiopathic dilated cardiomyopathy are evaluated and a method of predicting heart weight using QRS amplitudes is described. In 34 patients with multiple electrocardiograms (mean 3/patient) progressive prolongation of PR interval (0.18 +/- 0.03 to 0.21 +/- 0.03, p less than 0.001) and QRS duration (0.10 +/- 0.02 to 0.13 +/- 0.03, p less than 0.0001) was noted. Progressive conduction abnormalities were common (82%). QTc interval and QRS- and T-wave axes did not change. In 50 patients with electrocardiograms within 60 days of death, total 12-lead QRS and V1 through V6 QRS amplitude correlated better with heart weight (r = 0.51, p less than 0.0001 and r = 0.55, p less than 0.0001) than the Estes-Romhilt score did. The mean total 12-lead QRS amplitude was 138 mm with a mean of 106 for V1 through V6. In 31 patients cardiac mass index was calculated and showed significant correlation with 12-lead and V1 through V6 QRS amplitudes (r = 0.68, p less than 0.0001 and r = 0.75, p less than 0.0001, respectively). The QRS amplitudes remained constant during the illness. By using total 12-lead QRS or frontal plane QRS amplitude, heart weight can be predicted as early as 2 years before death. Use of body surface area and QRS amplitude criteria increases the accuracy of heart weight prediction. Thus, progressive electrocardiographic changes are common in patients with idiopathic dilated cardiomyopathy and QRS amplitude criteria are more accurate in the prediction of left ventricular hypertrophy than standard criteria.

Left bundle branch block with right axis deviation: a marker of congestive cardiomyopathy

Three patients with primary congestive cardiomyopathy (COCM), complete left bundle branch block (LBBB) and right axis deviation in the standard leads are described. Review of 50 additional patients from the literature since 1950 indicates that the uncommon combination of LBBB and RAD is a marker of severe myocardial disease, especially COCM. The mechanism of production of this electrocardiographic pattern appears to be diffuse conduction system involvement in advanced myocardial disease.

Significance of ventricular arrhythmias in idiopathic dilated cardiomyopathy

The incidence and prognostic significance of ventricular arrhythmias identified by 24-hour ambulatory electrocardiography (Holter) was prospectively assessed in 74 patients with idiopathic dilated cardiomyopathy (IDC). The criteria for diagnosis of IDC were based on clinical and cardiac catheterization findings. Holter monitoring was performed at the time of entry into the study. Patients were followed for 2 to 21 months (mean 11 +/- 3). Frequent ventricular premature complexes (VPCs) (greater than 1,000/24 hours) were seen in 35%, and complex VPCs (Lown grade III and IV) in 87% of the patients. Forty-nine percent of the patients had nonsustained ventricular tachycardia (VT) consisting of 3 to 32 beats with rates from 110 to 230 beats/min, and 20% had ventricular pairs. No correlation was found between clinical symptoms or the degree of left ventricular (LV) impairment and the number of ventricular pairs or episodes of VT. During follow-up, 19 patients died, 7 from congestive heart failure (CHF) and 12 suddenly. Patients who died suddenly had significantly more episodes of VT, ventricular pairs or total VPCs (p less than 0.01 each) compared with survivors and those who died from CHF. No significant differences were found between patients who died from CHF or suddenly with respect to LV end-diastolic pressure, LV end-diastolic volume index, LV ejection fraction (EF) and cardiac index. A linear stepwise discriminant function analysis using hemodynamic (LVEF and cardiac index) and arrhythmic (number of VT episodes and ventricular pairs) variables resulted in a meaningful separation between survivors and patients who died from CHF or suddenly.(ABSTRACT TRUNCATED AT 250 WORDS)

Significance of ventricular tachycardia in idiopathic dilated cardiomyopathy: observations in 35 patients

To evaluate the significance of ventricular tachycardia (VT) in idiopathic dilated cardiomyopathy (IDC), 35 consecutive patients seen between 1976 and 1980 were studied. The criteria for diagnosis of IDC were based on clinical, laboratory, and cardiac catheterization findings. All patients had right and left heart catheterization, left ventriculography, and coronary cineangiography. Long-term ambulatory electrocardiograms (Holter) were obtained in all patients at the time of diagnosis. There were 24 male and 11 female patients aged 22 to 72 years (mean +/- standard deviation [SD]51 +/- 12). Frequent ventricular premature beats (VPB) (30/h) were observed in 29 patients (83%): complex VPB (Lown grades 3, 4, and 5) in 93% and simple VPB in 7%. Twenty-one patients (60%) had nonsustained VT consisting of 3 to 46 beats (8 +/- 5) with rates from 75 to 210/min. No difference between patients with and those without VT was observed in regard to the presenting symptoms, functional classification, electrocardiographic findings, heart size on chest X-ray, and the hemodynamic measurements including cardiac index, left ventricular end-diastolic pressure, and ejection fraction. Patients with VT were older (p less than 0.05). Follow-up observation from 4 to 74 months (34 +/- 17) showed that 2 patients died suddenly (1 with and 1 without previous VT), a third patient died from intractable congestive heart failure, and the fourth from sepsis. It is concluded that (1) the incidence of ventricular arrhythmias in IDC is high, (2) VT is frequent and tends to occur in the nonsustained form, and (3) there is no correlation between VT and the clinical and hemodynamic findings. VT does not appear to predict prognosis during a relatively short follow-up period in patients with IDC.

Prognosis and possible presymptomatic manifestations of congestive cardiomyopathy (COCM)

In order to find evidence of prognosis and of presymptomatic manifestation of congestive cardiomyopathy (COCM) in fifty-eight patients, the extent of morphological changes of endomyocardial catheter biopsy (EMCB), clinical and haemodynamic data were correlated to the clinical course. In addition, clinical, haemodynamic, angiographic, morphological and His-bundle electrographic studies were performed in patients with left bundle branch block (LBBB), normal left ventricular end-diastolic volume, and normal coronary arteries (n = 43). Related to a 10-year mortality rate of 70% from the onset of symptoms, COCM is one of the most severe heart diseases. Endomyocardial catheter biopsy (EMCB) allowed clear prognostic separation in patients with COCM and seems to be of diagnostic value in patients with only slightly enlarged hearts and in patients with a short history of symptoms. The studies also revealed much evidence that at least some patients with LBBB, normal left ventricular end-diastolic volume (LVEDV) and normal coronary arteries exhibit an early stage of COCM. In these patients especially EMCB with severe changes of heart muscle cells and/or impaired left ventricular function may indicate subsequent COCM. So that there is now a new indication for performing EMCB.

TQ-ST segment mapping: critical review and analysis of current concepts

Controversy and confusion surround many aspects of TQ-ST segment mapping today. Technical standards pertaining to the recording and measurement of the TQ-ST deflection have not been uniformly established nor has the correlative value of the deflection as an indicator of myocardial injury been clearly ascertained. The TQ-ST deflection is believed to originate primarily although not exclusively as a result of extracellular potassium accumulation in the ischemic region and subsequent establishment of a transmembrane potential gradient during diastole and systole at the ischemic boundary. Nonspatial factors (including electrolytes, antiarrhythmic agents, heart rate) influence the TQ-ST deflection by altering this gradient. Spatial factors (including ischemic area and shape, electrode location) alter the relative position of the ischemic boundary to the electrode site and as such can be analyzed with the solid angle theorem. Further study of the complex behavior of the TQ-ST segment deflection, particularly in the presence of pharmacologic intervention, is necessary before mapping techniques can be used reliably in clinical studies designed to quantitate and modify ischemic damage.

Electrocardiographic changes in cardiomyopathic Syrian hamsters (strain BIO 8262)

Under ether anesthesia electrocardiograms were derived from Syrian hamsters (strain BIO 8262) suffering from cardiomyopathy and muscular dystrophy. In addition, ventricular weights and body weight were determined. Young hamsters -- not yet showing morphological signs of the cardiomyopathy with the exception of possible left ventricular hypertrophy -- demonstrated only a longer ventricular activation time than normal hamsters. With the onset of cardiac necrotization left axis deviation in frontal plane projection and right bundle branch blocks are developing in the cardiomyopathic hamsters followed by first degree atrioventricular conduction defects. During the late stage of the cardiomyopathy left bundle branch blocks are additionally arising, while left ventricular hypertrophy is disappearing. Since no overt heart failure is occurring in this strain of cardiomyopathic hamsters, gradual development of high degree conduction defects is assumed to terminate their lives. The electrocardiographic pattern of the hamster cardiomyopathy fits partly into that of human primary as well as secondary cardiomyopathy. Nevertheless, it seems to form an entity of its own, as arrhythmias, higher degree atrioventricular conduction disturbances, typical signs of ventricular or septal hypertrophy, abnormal P and Q waves, ST segment and T wave changes are lacking.

Complex atrial dysrhythmias in a patient with congestive cardiomyopathy

A patient with primary cardiomyopathy and long standing atrial fibrillation presented with atrial tachycardia and AV block. Atrial pacing sequentially converted the atrial tachycardia to atrial flutter (biatrial) and to the dissimilar atrial rhythms of right atrial fibrillation with left atrial flutter, right atrial flutter with left atrial electrical standstill and right atrial fibrillation with left atrial standstill. The clincial milieu and intracardiac recordings are presented.

Idiopathic ventricular tachycardia. An intracardiac electrical, hemodynamic and angiographic assessment of six patients

Six patients with idiopathic paroxysmal ventricular tachycardia were investigated by external electrocardiography, intracardiac electrography and pacing, exercise testing, cardiac catheterization and coronary angiography. All had normal hemodynamics and coronary arteries. His bundle electrography proved ventricular origin in five; one had no paroxysmal ventricular tachycardia during His bundle electrography. Treatment with diphenylhydantoin, 4.2 to 8.0 mg/kg/day, and propranolol, 0.8 to 2.7 mg/kg/day, appeared effective, well tolerated therapy in three, and procainamide and propranolol in one requiring medical treatment. Abstinence from tobacco and coffee abolished paroxysmal ventricular tachycardia in one of two who required no medication. The other has no recurrence of paroxysmal ventricular tachycardia since study.