A method of diagnosing heart disease, the method comprising: (a) extracting DNA from extracellular vesicles isolated from a subject sample; (b) performing polymerase chain reaction on the extracted DNA using a pair of primers having SEQ ID NO: 1 and SEQ ID NO: 2; and (c) comparing an increase or decrease in content of bacteria-derived extracellular vesicles of the subject sample with that of a normal individual-derived sample through sequencing of a product of the PCR, wherein the subject sample is blood; wherein the heart disease is myocardial infarction, cardiomyopathy, variant angina, or atrial fibrillation; and wherein, in process (c), myocardial infarction is predicted by comparing an increase or decrease in content of extracellular vesicles derived from one or more bacteria selected from the group consisting of the genus Salinispora, the genus Candidatus Solibacter, the genus Citrobacter, the genus Collinsella, the genus Burkholderia, the genus Coprococcus, the genus Rhodoplanes, the genus Propionibacterium, the genus Methanobacterium, the genus Methanocella, the genus Streptacidiphilus, the genus Streptomyces, the genus Methanosaeta, and the genus Lysinibacillus; or wherein, in process (c), cardiomyopathy is predicted by comparing an increase or decrease in content of extracellular vesicles derived from one or more bacteria selected from the group consisting of the genus Sphingomonas, the genus Thermoanaerobacterium, the genus Neisseria, the genus Turicibacter, and the genus Phascolarctobacterium; or wherein, in process (c), variant angina is predicted by comparing an increase or decrease in content of extracellular vesicles derived from one or more bacteria selected from the group consisting of the genus Catenibacterium, the genus Deinococcus, the genus Fusobacterium, and the genus Adlercreutzia; or wherein, in process (c), atrial fibrillation is predicted by comparing an increase or decrease in content of extracellular vesicles derived from one or more bacteria selected from the group consisting of the genus Chryseobacterium, the genus Enterococcus, the genus Alcanivorax, the genus Psychrobacter, the genus Bacteroides, the genus Geobacillus, the genus Haemophilus, the genus Veillonella, the genus Paracoccus, the genus Halomonas, the genus Ruminococcus, and the genus Porphyromonas. (a) extracting DNA from extracellular vesicles isolated from a subject sample; (b) performing polymerase chain reaction on the extracted DNA using a pair of primers having SEQ ID NO: 1 and SEQ ID NO: 2; and (c) comparing an increase or decrease in content of bacteria-derived extracellular vesicles of the subject sample with that of a normal individual-derived sample through sequencing of a product of the PCR, wherein the subject sample is blood; wherein the heart disease is myocardial infarction, cardiomyopathy, variant angina, or atrial fibrillation; and wherein, in process (c), myocardial infarction is predicted by comparing an increase or decrease in content of extracellular vesicles derived from one or more bacteria selected from the group consisting of the genus Salinispora, the genus Candidatus Solibacter, the genus Citrobacter, the genus Collinsella, the genus Burkholderia, the genus Coprococcus, the genus Rhodoplanes, the genus Propionibacterium, the genus Methanobacterium, the genus Methanocella, the genus Streptacidiphilus, the genus Streptomyces, the genus Methanosaeta, and the genus Lysinibacillus; or wherein, in process (c), cardiomyopathy is predicted by comparing an increase or decrease in content of extracellular vesicles derived from one or more bacteria selected from the group consisting of the genus Sphingomonas, the genus Thermoanaerobacterium, the genus Neisseria, the genus Turicibacter, and the genus Phascolarctobacterium; or wherein, in process (c), variant angina is predicted by comparing an increase or decrease in content of extracellular vesicles derived from one or more bacteria selected from the group consisting of the genus Catenibacterium, the genus Deinococcus, the genus Fusobacterium, and the genus Adlercreutzia; or wherein, in process (c), atrial fibrillation is predicted by comparing an increase or decrease in content of extracellular vesicles derived from one or more bacteria selected from the group consisting of the genus Chryseobacterium, the genus Enterococcus, the genus Alcanivorax, the genus Psychrobacter, the genus Bacteroides, the genus Geobacillus, the genus Haemophilus, the genus Veillonella, the genus Paracoccus, the genus Halomonas, the genus Ruminococcus, and the genus Porphyromonas.