Evaluation of myocardial ischemia in Kawasaki disease by dobutamine stress signal-averaged ventricular late potentials

Biopsy-proven myocardial sequels in Kawasaki disease with giant coronary aneurysms

BACKGROUND

Although most Kawasaki disease with giant coronary aneurysms is asymptomatic, conventional investigations might not identify previous lesions, or all Kawasaki disease with giant aneurysms at risk of future myocardial lesions. We evaluated the long-term histopathology of the myocardium, especially of intramural small vessels in asymptomatic Kawasaki disease with giant aneurysms.

METHOD

The initial study comprised 16 consecutive Kawasaki patients - male-to-female ratio was 12:4 - aged from 2 to 12 years, and in the subsequent study, the same patients were aged from 4.9 to 16 years. Endomyocardial biopsies were histopathologically evaluated. Microangiopathies, mitochondrial abnormalities, and loss or disarray of myofibrils were compared by electron microscopy.

RESULTS

The incidence of histopathological abnormalities such as degeneration, hypertrophy, and inflammatory cell infiltration was quite high in the initial study, and inflammatory cell infiltration, interstitial fibrosis, and disarray were very noticeable at follow-up biopsies. The area of fibrous tissue was significantly higher in patients administered with intravenous immunoglobulin at follow-up biopsies. Electron microscopy showed microangiopathies including microthrombi within intramural small vessels in some patients at follow-up biopsies. The sites of the coronary aneurysms did not seem to have an impact on the biopsy findings, suggesting that the underlying pathophysiology is related to the original disease process.

CONCLUSIONS

Whether the abnormalities were due to direct myocardial injury, chronic ischaemia, repeated small-vessel thrombosis, or other problems associated only with biopsies, is difficult to determine. However, this subgroup had residual abnormal lesions in the myocardium. Follow-up should be more aggressive in this group of patients to identify myocardial damage that could be asymptomatic.

Application of signal-averaged electrocardiogram to myocardial damage in the late stage of Kawasaki disease

BACKGROUND

Myocardial damage occurs in the late stage of Kawasaki disease (KD) regardless of whether coronary artery lesions (CALs) are present.

METHODS AND RESULTS

A signal-averaged electrocardiogram (ECG) was performed in 23 patients who were in the late stage of KD (CAL was found in 12 and no CAL (non-CAL) was found in 11) and 10 healthy controls. Filtered QRS duration and the root-mean-square voltage in the last 40 ms of the QRS complex were measured using time-domain analysis. Additionally, the area ratio (AR), (area of 20-50 Hz)/(area of 0-20 Hz) x100, was calculated by frequency domain analysis. These findings were compared with the clinical data and histopathological findings. In time-domain analysis, there were no significant differences among the 3 groups. In frequency domain analysis, the AR in CAL was significantly higher than that in the other 2 groups. Furthermore, all 4 patients who underwent an endomyocardial biopsy showed a high AR and abnormal histopathological features.

CONCLUSIONS

The findings of the present study suggest that patients in the late stage of KD have abnormal findings on signal-averaged ECG even without stenotic lesions, arrhythmia or ischemia, a condition that might reflect histopathological changes in the myocardium in the late stage of KD.

Lack of impact of myocardial ischemia on the signal-averaged ECG assessment by time-domain analysis

BACKGROUND

Late potentials represent an arrhythmogenic substrate in chronically infarcted myocardium. It is hypothesized that acute transient ischemia enhances anisotropic electrical ventricular activation and facilitates reentry mechanisms. Study aim was the prospective assessment of the impact of dipyridamole-induced myocardial ischemia on the signal-averaged ECG.

METHODS

Dipyridamole stress thallium-201 SPECT imaging was utilized to avoid noise contamination of the signal-averaged ECG from exercise and to document evidence and localization of myocardial ischemia or persistent perfusion defects in 68 patients with suspected coronary artery disease. Before and during dipyridamole-induced vasodilatation serial signal-averaged ECG was performed to evaluate the influence of transient ischemia on the occurrence of late potentials.

RESULTS

There was a significant difference between heart rate at rest and heart rate under dipyridamole influence in patients with inducible ischemia (70 +/- 13 vs. 87 +/- 13; P < 0.0001) in contrast to patients without dipyridamole-induced ischemia (74 +/- 20 vs. 80 +/- 16; n.s.). The number of averaged beats and achieved noise level was comparable between both groups. Thirty-three of 68 patients (49%) revealed dipyridamole-induced ischemia; however, no changes of the SAECG parameters, such as QRS, RMS, LAS at 25-250 and 40-250 Hz bandpass filtering in the leads X, Y, Z and vector magnitude, respectively, were observed as a result of ischemia.

CONCLUSION

These results suggest that transient myocardial ischemia does not affect the signal-averaged ECG. Clinically, the signal-averaged ECG analysis seems not to be helpful in identifying patients with silent ischemia.

Evaluation of cardiac reserved function by high-dose dobutamine-stress echocardiography in asymptomatic anthracycline-treated survivors of childhood cancer

BACKGROUND

The aim of this study was to evaluate cardiac function and cardiac reserved function in asymptomatic anthracycline-treated long-time survivors of childhood cancer using dobutamine (DOB) stress echocardiography.

METHODS

A total of 26 patients (19 males and 7 females) were divided into four groups according to cumulative dose of anthracycline (ATC): non-anthracycline group (N group), seven cases; low anthracycline cumulative dose group (L group), five cases (<or=200 mg/m(2)); medium anthracycline cumulative dose group (M group), seven cases (200-<400 mg/m(2)); high anthracycline group (H group), seven cases (>or=400 mg/m(2)). DOB infusion was begun at 5 microg/kg per min (gamma) and increased up to 30 gamma. Cardiac function and cardiac reserved function at rest, after low-dose and high-dose DOB stress, were estimated.

RESULTS

In the H group, % left ventricular posterior wall thickening (%PWT) at rest and ratio of maximum early filling peak velocity (E) and atrial contraction peak velocity (A) from the left ventricular transmitral flow wave (E/A) and %PWT at DOB 5 gamma stress were significantly lower than in other groups (P<0.05). After DOB 30 gamma stress in groups given>00 mg/m(2) end-systolic wall stress was significantly higher and E/A and %PWT were significantly lower than those of other groups (P<0.05). ATC cumulative dose strongly correlated with %PWT after DOB 30 gamma stress (P<0.001).

CONCLUSIONS

Subclinical ATC cardiotoxicity was detected by high-dose DOB stress echocardiography at lower cumulative doses than with other methods. %PWT appears to be a useful index for detection of ATC cardiotoxicity.

Dobutamine stress surface mapping of myocardial ischemia in Kawasaki disease

BACKGROUND

To detect and localize myocardial ischemia, a method that does not require physical exertion is sometimes needed in children with Kawasaki disease.

METHODS

Dobutamine stress body surface mapping was performed in 115 children with a history of Kawasaki disease (58 without coronary artery lesions, 40 who had coronary lesions without myocardial ischemia and 17 with myocardial ischemia). The maximum infusion rate of dobutamine was 30 microg/kg per min. Myocardial ischemia was diagnosed by the presence of an area of hypoperfusion on scintigraphy at rest and/or an increase in hypoperfusion during a dobutamine stress test compared with resting scintigraphy. We studied the number of leads that showed significant ST depression on the isopotential map (nST), the number of the row containing the lead with the smallest negative value on the isointegral map (I(min)), and the localization of myocardial ischemia on the isointegral map. Based on findings in patients without coronary artery lesions, we defined the criteria for detecting myocardial ischemia as nST > or = 1 and I(min) < or = 4.

RESULTS

The sensitivity of detecting myocardial ischemia was 94.1% using nST and 41.7% using I(min), while the specificity of these methods was 98.9 and 96.9%, respectively. The localization of myocardial ischemia on stress body surface mapping was 100% concordant with that determined by stress myocardial scintigraphy.

CONCLUSIONS

Dobutamine stress body surface mapping for the detection of myocardial ischemia is a non-invasive, more convenient and repeatable test compared with exercise myocardial scintigraphy and it is a more objective test compared with exercise echocardiography. Dobutamine stress body surface mapping is useful for the identification and localization of silent myocardial ischemia in pediatric patients with Kawasaki disease, especially those who cannot perform tests involving physical exercise.

Kawasaki disease

Kawasaki disease is a leading cause of acquired heart disease in children in the USA. An acute vasculitis of unknown etiology, it occurs predominantly in infancy and early childhood, and more rarely in teenagers. Coronary artery aneurysms or ectasia develop in approximately 15-25% of children with the disease. Treatment with intravenous gamma globulin, 2 g per kg, in the acute phase reduces this risk three- to fivefold. Angiographic resolution occurs in approximately one-half of aneurysmal arterial segments, but these show persistent histologic and functional abnormalities. The remainder continue to be aneurysmal, often with development of progressive stenosis or occlusion. The worst prognosis occurs in children with so-called 'giant aneurysms', i.e. those with a maximum diameter greater than 8 mm, because thrombosis is promoted both by sluggish blood flow within the massively dilated vascular space and by the frequent development of stenotic lesions. Serial stress tests with myocardial imaging are mandatory in the management of patients with Kawasaki disease and significant coronary artery disease to determine the need for coronary angiography and transcatheter interventions or coronary bypass surgery. Continued long-term surveillance in patients with and without detected coronary abnormalities is necessary to determine the natural history of Kawasaki disease.