A cardiac imaging technique comprises (a) introducing a sufficient quantity of a not highly attenuating gas into the stomach of a patient to distend the stomach wall of the patient; and (b) while the stomach wall of the patient is distended, performing radionuclide imaging of the heart and/or of the heart's contents. Preferably, the gas used to distend the stomach wall is introduced into the patient (i) by having the patient ingest a substance that, when contacted with water or with stomach contents, produces the gas, (ii) by having the patient imbibe a liquid which has been mixed or combined with a gas-producing substance, or (iii) by having the patient imbibe a liquid into which the gas has been dissolved.