The conclusion from the abstract: "After adjustment for traditional cardiovascular risk factors, a genetic risk score comprising 101 single nucleotide polymorphisms was not significantly associated with the incidence of total cardiovascular disease."
Since traditional risk factors include family history, it's totally unsurprising that a mere 101 genetic variants cannot beat them out. Since novel deleterious mutations in cardiovascular genes are rare (human mutation rate is ~10E-8 per nucleotide per generation; unpublished data) your family history contains virtually all of the information you're going to get from genetics.
Also, we're talking about 101 common genetic associations - not 101 genes. To put this in perspective, APOB itself has over 101 known deleterious variants itself. They didn't test all of these; they just tested 101 common-variant, disease-associated SNPs. So the study is actually much less interesting than it might be.
EDIT: Oh, not to mention that traditional risk factors include things like LDL-cholesterol, the best-established causal risk factor for MI. The genetic risk score includes many SNPs that influence LDL-C level. LDL-C is ~50% genetically determined, 50% environmental. So knowing the LDL-C level is, unsurprisingly, a more powerful predictor of MI risk than is knowledge of the variants that influence LDL-C.