Avanindra Jain

Coronary artery fistula: an abnormality affecting all age groups.

A coronary artery fistula is an abnormal communication between a coronary artery and a cardiac chamber, great vessel, or other vascular structure. It is an infrequent but potentially important abnormality that can affect any age group. Most are congenital in origin, although other etiologies, in particular trauma, have been identified. Many are small and found incidentally during coronary arteriography, while others are identified as the cause of a continuous murmur, myocardial ischemia, congestive heart failure, or, rarely, bacterial endocarditis. The diagnosis should be considered in any patient presenting with a continuous murmur or in the setting of congestive heart failure, myocardial ischemia, or bacterial endocarditis without an obvious etiology. The pathophysiologic mechanisms resulting in symptoms include cardiac volume overload due to the shunting of blood and reduction of the myocardial blood supply due to coronary steal. The diagnosis of coronary artery fistula may be suggested by the finding of a continuous murmur in a precordial location, which is atypical for patent ductus arteriosus. Two-dimensional echocardiography may demonstrate dilated coronary arteries, and pulse-wave and color-flow Doppler examinations can display turbulent flow in the suspected fistula and its receiving chamber or vessel. Angiography is generally needed to confirm the diagnosis and elucidate anatomic detail. The natural history of coronary artery fistula is variable, with long periods of stability in some patients and gradual progression of symptoms in others. Small fistulas detected incidentally at the time of angiography do not require immediate surgical correction, but careful follow-up is indicated because the potential for enlargement with physiologically important shunting exists and cannot readily be predicted. Spontaneous closure is uncommon. Surgical repair of the fistula is recommended for symptomatic patients and for some without symptoms because a quantitatively small shunt does not predict freedom from future symptoms or complications. Those selected for medical management must be followed closely.

Lack of specificity of new negative U waves for anterior myocardial ischemia as evidenced by intracoronary electrogram during balloon angioplasty

Negative U waves on the surface electrocardiogram are reported to be a specific marker of myocardial disease. In the setting of ischemia, they correlate with stenosis of the left main and left anterior descending coronary arteries. To determine whether U wave changes are unique for anterior ischemia, the development of new U waves on the intracoronary electrogram was correlated with the location and magnitude of ischemia during coronary balloon angioplasty. Recordings were obtained during dilation of 43 vessels in 37 patients. New negative U waves developed during dilation of 12 vessels (7 of the left anterior descending, 4 of the left circumflex and 1 of the right coronary artery). New positive U waves developed during dilation of 18 vessels (12 of the left anterior descending, 3 of the left circumflex and 3 of the right coronary artery). The magnitude of ST segment change was 10.9 +/- 6.7 mm in the presence of a new U wave but only 3.4 +/- 2.8 mm in the absence of a new U wave (p less than 0.001). It is concluded that 1) negative U waves on the intracoronary electrogram are not specific for anterior ischemia; 2) new positive U waves on the intracoronary electrogram are as sensitive as new negative U waves for acute ischemia; 3) the development of a new positive or negative U wave is associated with the magnitude of myocardial ischemia; and 4) the recording of U waves may be related to the proximity of the recording leads to the location of ischemia.

Comparison of early exercise treadmill test and oral dipyridamole thallium-201 tomography for the identification of jeopardized myocardium in patients receiving thrombolytic therapy for acute Q-wave myocardial infarction☆

Thrombolytic therapy has become the treatment of choice for patients with acute myocardial infarction. Researchers are not yet able to identify patients with salvage of myocardium who are at risk for recurrent coronary events. Thus, a prospective trial was performed in 46 patients with myocardial infarction (28 anterior and 18 inferior) who received thrombolytic therapy to determine if early thallium tomography (4.7 days) using oral dipyridamole would identify more patients with residual ischemia than early symptom-limited exercise treadmill tests (5.5 days). There were no complications during the exercise treadmill tests or oral dipyridamole thallium tomography. Mean duration of exercise was 11 +/- 3 minutes and the peak heart rate was 126 beats/min. Thirteen patients had positive test results. After oral dipyridamole all patients had abnormal thallium uptake on the early images. Positive scans with partial filling in of the initial perfusion defects were evident in 34 patients. Angina developed in 13 patients and was easily reversed with intravenous aminophylline. Both symptom-limited exercise treadmill tests and thallium tomography using oral dipyridamole were safely performed early after myocardial infarction in patients receiving thrombolytic therapy. Thallium tomography identified more patients with residual ischemia than exercise treadmill tests (74 vs 28%). Further studies are required to determine whether the results of thallium tomography after oral dipyridamole can be used to optimize patient management and eliminate the need for coronary angiography in some patients.

Induction of ventricular tachycardia in patients with left ventricular aneurysms and no history of arrhythmia

We recently reported 5 patients who developed sustained entricular tachycardia (VT) for the first time after a left ventricular (LV) aneurysmectomy performed for nonarrhythmic indications.1 It was unclear whether the aneurysmectomy directly precipitated the arrhythmia in those patients, or simply failed to remove a preexisting VT substrate. If the latter were true, recognition of the substrate before surgery and ablation by endocardial resection at the time of aneurysmectomy2,3 could have prevented the postoperative arrhythmia. Therefore, the current study was undertaken to determine how often aneurysms provide a substrate for VT detectable by programmed stimulation and whether any clinical or angiographic variables predict arrhythmia inducibility.

Patterns of ST-segment change during acute no-flow myocardial ischemia produced by balloon occlusion during angioplasty of the left anterior descending coronary artery.

Abstract An early manifestation of acute myocardial ischemia is the development of ST-segment and T-wave changes. Clinical decisions for treatment are based on ST-segment shifts on the surface electrocardiogram (ECG). ST-segment depression is believed to represent subendocardial involvement, with less extensive myocardial injury. ST-segment elevation reflects transmural involvement, with greater extent of myocardial injury. 1−3 ST-segment depression is generally induced by factors that increase myocardial demand, such as atrial pacing or exercise stress, whereas ST-segment elevation is induced by near total cessation of coronary blood flow. After acute total occlusion of the vessel, myocardial injury is believed to progress from the endocardium to the epicardial layers. Thus, we would expect to observe ST-segment depression progressing through an isoelectric point to ST-segment elevation. This may explain why some patients have no significant changes on the ECG when presenting with an acute myocardial infarction. To test this hypothesis in humans, we used balloon angioplasty of the coronary arteries as the model for acute noflow ischemia. Intracoronary electrograms were obtained from the center of the ischemic zone by attaching the proximal end of the balloon angioplasty guidewire to the V 1 lead on the surface ECG. Patterns of ST-segment responses on the intracoronary electrogram and surface leads II and V 5 were continuously recorded.

Reduction in radiation exposure during coronary angiography

In addition to lead shielding, increased distance between the operator and x-ray source will lower radiation exposure. To utilize this principle, we interposed a 24 in. piece of pressure tubing between the catheter used for coronary angiography and the manifold apparatus. Radiation exposure to the hand of the operator during coronary angiography was compared with and without the extension tubing. When corrected for the differences in exposure time, operator exposure was 5.38 mrem/min without the extension and 4.84 mrem/min with the extension. Although this is a small difference in exposure/min, a substantial reduction in exposure could accumulate over a 1 yr period. Insertion of this extension tube into the catheter system is a simple and safe way to further reduce operator exposure during coronary angiography.

Limitations of the metabolic rate meter for measuring oxygen consumption and cardiac output

Over the past few years, a metabolic rate meter has been introduced for easy measurement of oxygen consumption. However, its accuracy is unproved. In 40 patients (26 men, 14 women, ages 34 to 73 years), cardiac output was measured simultaneously by thermodilution and the Fick method using the metabolic rate meter to quantitate oxygen consumption. In comparison with thermodilution, the results using the Fick method were low (5.26 +/- 1.18 vs 4.14 +/- 0.99 liters/min, respectively, p less than 0.01). In 18 patients cardiac output also was measured by the Fick method using a Douglas bag to quantitate oxygen consumption. In these patients, oxygen consumption measured with the metabolic rate meter was lower than that obtained using the Douglas bag (168 +/- 25 vs 216 +/- 42 ml/min, respectively, p less than 0.01). With the Douglas bag, the Fick and thermodilution cardiac output measurements were similar (4.68 +/- 1.08 vs 4.87 +/- 0.86 liters/min, respectively, difference not significant), and they differed by less than or equal to 10% in 15 patients. In contrast, with the metabolic rate meter, the results of thermodilution were higher than those with the Fick method (4.84 +/- 0.95 vs 3.60 +/- 0.71 liters/min, respectively, p less than 0.01), and differed by less than or equal to 10% in only 1 patient (p less than 0.01). Thus, the values for oxygen consumption and cardiac output obtained with the metabolic rate meter are lower than actual values. This device is less accurate than the Douglas bag.

Comparison of coronary angiography and early oral dipyridamole thallium-201 scintigraphy in patients receiving thrombolytic therapy for acute myocardial infarction

We evaluated 50 consecutive patients who received thrombolytic therapy for acute myocardial infarction using thallium-201 single photon emission computed tomography in combination with oral dipyridamole (300 mg) to assess the frequency of residual myocardial ischemia. Thallium studies were performed early after myocardial infarction at a mean of 4.6 days (range 3 to 11) in 50 patients. The time from the onset of chest pain to the administration of thrombolytic therapy was 2.6 hours (range 0.5 to 5.5). Q wave myocardial infarction was evident in 46 patients; four patients had a non-Q wave infarction (anterior infarction in 31 patients and inferior infarction in 19 patients). The serum mean peak creatinine kinase was 1503 IU/L (range 127 to 6500). Coronary angiography was performed in all patients at a mean of 3.1 days (range 2 to 10) and revealed the infarct-related vessel to be patent in 36 patients (72%). The ejection fraction was 48% (range 26% to 67%). After dipyridamole administration, 13 patients (26%) developed angina that was easily reversed with the administration of intravenous aminophylline. Systolic blood pressure decreased from 122 to 115 mm Hg (p less than 0.05) and the heart rate increased from 76 to 85 beats/min (p less than 0.05). None of the patients had significant hypotension, arrhythmias, or evidence of infarct extension. Perfusion abnormalities were present on the initial thallium images in 48 patients. Redistribution suggestive of ischemia was present in 36 patients (72%). Ischemia confined to the vascular distribution of the infarct vessel was evident in 22 patients. Seven patients had ischemia in the infarct zone as well as in a remote myocardial segment. Thus 29 patients (58%) had ischemia in the distribution of the infarct vessel. Ischemia in the infarct zone was evident in 19 of 36 patients (53%) with open infarct vessels and in 10 of 14 patients (71%) with occluded infarct vessels. In conclusion, thallium-201 single photon emission computed tomography using oral dipyridamole was safely performed in patients with recent myocardial infarctions who receive thrombolytic therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of coronary angiographic features and oral dipyridamole thallium 201 tomography

Coronary angiography and left ventriculography is commonly used to identify those patients with incomplete infarctions and therefore, a need for revascular ization. The authors compared coronary angiography and left ventriculography with thalliumm 201 tomography using oral dipyridamole to identify patients with potential ischemia in the infarct zone indicating viable tissue. Forty-five patients (37 men, 8 women) with acute myocardial infarctions (29 anterior, 16 inferior) who received intravenous thrombolytic therapy were studied. On the basis of the left ventriculograms, only 16 patients were judged to have residual function in the infarct zone . Six of these patients had no thallium redistribution in the infarct zone, indicating lack of residual ischemia. Of the 29 patients with no residual function in the infarct zone, 18 had redistribution in the infarct zone, suggesting residual ischemic myocardium and thus viable tissue . Among the 32 patients with open infarct vessels, 15 had no redistribution in the infarct zone, but of the remaining 13 patients with occluded infarct vessels, 9 had redistribution in the infarct zone indicating residual ischemia and thus viable tissue . The authors data suggest that neither wall motion analysis by left ventriculography nor the an giographic status of the infarct vessel identifies those patients with residual ischemia as evidenced by thallium tomography using oral dipyridamole.

Usefulness of coronary angiography in patients requiring repeat cardiac valve surgery

Abstract Widespread application of surgical treatment for valvular heart disease has made the diagnosis of prosthetic valve dysfunction of great clinical importance. Recent advances in cardiac imaging techniques, including color Doppler and transesophageal echocafdiography, provide such a detailed picture of valve anatomy and function that often cardiac catheterization adds little to the assessment. 1,2 Despite adequate noninvasive assessment of prosthetic valve function, adult patients continue to undergo cardiac catheterization before reoperation to rule out the development of new significant coronary artery disease. This is usually performed even if the patient has been shown to be free of coronary artery disease at the time of initial valve surgery. The frequency with which significant coronary artery disease develops or progresses in patients with valvular heart disease and the diagnostic yield of repeat coronary arteriography have not been adequately defined. This study examines a consecutive series of patients with prosthetic heart valves who underwent cardiac catheterization for recurrent symptoms to determine (1) the frequency with which new significant coronary disease develops in patients without previous disease, (2) the frequency with which new significant lesions appear in patients with known disease, and (3) clinical parameters that may identify patients with new significant coronary artery disease.